Protein Metabolism for First BDS students according to MUHS syllabus.

1. PROTEIN METABOLISM:
FOR FIRST BDS
Dr. Smita Pakhmode
NKP SIMS & RC, Nagpur.

2. PROTEIN METABOLISM:
Syllabus
• Digestion & Absorption,
• Deamination, Transamination.
• Ammonia metabolism, Urea formation.
• Transmethylation. Formation of amines.
• Phospho creatine formation.
• Introduction to other functions of aromatic
amino acids
• One carbon transfer.

3. Lets recap about protein..
• Definition protein
• Amino acids
• Functions of protein

4. Protein Turnover
• Continuous degradation and resynthesis
of all cellular proteins.
Body Proteins
Amino Acids
1-2% Pr.
Degradtion
20-25% Catabolism to
form urea
75-80% for
New pr.
Synthesis

5. Phases of Protein metabolism
Dietary proteins
50-75gm/day
Breakdown of Tissue
proteins( 300-400g)
Amino Acid POOL
(100g)
Synth. Of Body
Proteins.
(300-400 g/day)
-Stru. Tissue pro.
-Hb
-Plasma Proteins
-Enzyme
-Milk
-Hormones.
Exess AA
Renal Excretion
0.9-1 G/day
Synth. Of NPN/
specialized products
-Hormones.
Cholin(Bile Acid)
-Purines
-Coenzyme(Niacin)
-Serotonin,Melatonin
-Heme
-Creatin
-Phospholipids
-Detoxification product
TA
DA
Keto Acids
Urea(15 to 30g/d)
Ammonia
Gluconeo
genesis
Non
Essential
AA
Oxidation

6. Nitrogen balance:
Dietary pro
Biosynthesis
of Proteins
Urea(Urine) Sweat Faeces.
Positive N2 Balance:
Growing age, Puberty,
tissue repair after surgery
or trauma
Negative N2 balance:
fever, starvation, cachexia
Covalscence , Cancer
Amino
Acids
Total BUN excretion : 10-20g urea N2/Day
Creatinine:1 to 1.5gms/day
Uric Acid:500 to 700 mg/day
Ammonium Ions: 140 to 1500 mg NH4 ions/day

7. Digestion & Absorption of
Proteins
• Starts in stomach & completes in lower
part of small intestine.
• Enzymes: Peptidases

8. Try, Trp,
PA,Met
& Leu
Chymotry
psin
Chymotry
psinogen
Ala,
Gly,
Ser
Elastase
Pro
Elastase
A_
Ala,Ile,Val
B_ Arg,
Lys
Carboxype
ptidse A &
B(exo)
ProCarbox
ypeptidse
A & B
Pancreas
Arg
Lys
Trypsin
Enteropeptidase
Trypsinogen
N………………..CONH………………….CONH………………CONH……………CONH
Collagenase, Elastocollagenase,
Mucoproteinase
Gastrin Cholecystokinin, Pancreozymin, Secretin
Digestion of proteins
HCl
Serine proteases

9. Absorption of
protein in Intestine
Enzymes: Aminopeptidases &
Dipeptidases
Absorption of Amino acid:
D AA acids absorbed by passive
diffusion.
L AA acids absorbed by active
diffusion.
1. Similar to Glu transport.(Na-K
pump transport)
2. γ Glutamyl cycle or Meister cycle.
3. Six different transport proteins
transfers different AA
• Short chain,neutral AA
• LC, neutral and aromatic AA
• Basic Amino acid
• Acidic AA
• Imino acids
• Beta amino acids
Free Amino Acids ,Dipeptides
are absorbed in small
intestine
Amino acids enters in portal
circulations and distributed different
tissues

10. Absorption of protein
Gamma Glutamyl Meister Cycle:
Intestine , Kidney tubules & Brain
ATP required process
Dependent on the Glutathion
Operates for Fast absorption of Glutamine & cysteine

11. Intracellular Degradation of
Protein
• Lysosomal Cathepsin mediated degradation.
(Cancers)
• Ubiquitin : Non lysosomal, ATP dependent
process
• Proteosome: cylindrical assembly which
segregated ubiquitin tagged proteins
(Alzheimer's, Parkinsonism, Huntington's disease
& Amyotropic Lateral sclerosis (ALS))

13. Disorders of Absorption of
protein
Food allergy : because of intact pr.
Absorption
Immunity transfer to fetus is due to
passage of IgA through colostrum
Cystinurea: Renal Calculi

15. Glucose Alanin Cycle
Glu
Pyruvate
NH3 Urea
Ala
Glu
Ala
Liver
Muscle
Glu
Pyruvate. LA
AA
KA
Alanine
2ATP
TA
Blood
6ATP
4ATP

16. Starvation phase
Well fed state phase

17. Urea biosynthesis
(Transamination & Deamination Reactions
of Amino Acids & transport of Ammonia)
Dr. Smita Pakhmode
NKP SIMS & RC, Nagpur
Protein Metabolism Lecture: 2
For First BDS students

18. Urea biosynthesis
• Urea biosynthesis occurs in four stages:
(1) transamination,
• (2) oxidative deamination of glutamate,
• (3) ammonia trans- port, and
• (4) reactions of the urea cycle

19. Amino -Keto Acid pairs
CH3—CH- COO -
|
NH3
+
CH3—C- COO-
||
O
OOC-CH2—CH- COO -
|
NH3
+
OOC-CH2-CH2—CH- COO -
|
NH3
+
OOC-CH2—C- COO-
||
O
OOC-CH2-CH2—C- COO -
||
O
PYRUVATE
ALANINE Aspartic Acid Glutamic Acid
Oxaloacetate
Alpha ketoglutarate

20. Catabolism of
Amino Acid
……..
AA
Keto Acid ( Carbon
skeleton)
Energy. Glucose. Fat NE AA
⍺ Keto glutarate
Deamination
Glutamate. NH3 Urea
Transamination
Dietary Protein. Body Protein
Pr.
Synthesis
Synthesis N
compound
NH4
Deamination

21. Transamination Reaction:
TRANSAMINATION
•Shuffling of amino group
•Cytosol & Mitochondrion
•Liver, kidney brain & Heart
•Only 3 ketoacids participate
• ⍺ KG, Py acid, OAA
•Enzyme – Transaminase
•Coenzyme – B6
•Roles of PLP
•Exception – Lysine & Threo, &
prolein
•Significance:
 Interconversion of AA
to AA in short supply
 Channel amino acid to
Glutamate /aspartate
 Connects between Carb & Pr.
metab Ping pong & Bi Bi Mechanism of
Transamination reaction
Process of Transamination

22. Transaminases of clinical
Significance
Aspartate. ⍶ KG
AST/ SGOT. PLP
Oxaloacetate Glutamate
Alanine. ⍶ KG
ALT/ SGPT. PLP
Pyruvate Glutamate
AST/ SGOT: Marker Enzyme for
Myocardial Tissues
↑ Myocardial Infarction, Liver
Disorders, Muscular dystrophies &
Myositis
ALT/ SGPT: Marker Enzyme for
Hepatic Tissues
↑ Hepatocellular damage, Acute
Viral Hepatitis.

23. Occurs in all tissues
Occurs in Liver

24. Deamination
Elimination of Amino group from Amino Acid to free Ammonia
is known as Deamination
NON Oxidative:
Deamination without
undergoing oxidation
Oxidative :
Liberation of ammonia from
Amino acid coupled with
oxidation

25. Oxidative Deamination
• Oxidative Deamination:
-Liberation of free ammonia from amino acid
coupled with oxidation.
Site:
Liver & Kidney
Imp:
Provides
NH3…….. For Urea synthesis
Keto acid……. Used in different reactions
Enzymes:
Glutamate Dehydrogenase
Amino acid Oxidase

26. OXIDATIVE DEAMINATION
1. GLUTAMATE DH [MAJOR]…….
Glutamate α – keto glutarate
H2O NH3
NAD(P) NAD(P)H + H+
Zn ++
Reversible Reaction
Mitochondion
Can Use NAD & NADP
Immunoglutarate is intermidiate.
ATP/GTP inhibits.
ADP/GDP stimulates.
Steroid & Thyroxin inhibit
GDH

27. OXIDATIVE DEAMINATION
2. L-AMINO ACID OXIDASE
L Amino acid α keto acid
H2O
NH3
FMN FMNH2
Zn ++
O2
H2O2
H2O
catalase
LAA Oxidase

28. D - AMINO ACID OXIDASE
DAAO uses FAD as a coenzyme.
D Amino Acid oxidases converts unnatural Amino acid in to LAA
which can undergo various process.
Activity of DAAO higher than LAAO
No production of NADH hence no formation of energy.
FAD FADH2

29. NON OXIDATIVE DEAMINATION
PLP
Threonine,
Homoserine
NH 4
NH 4

30. Name 2 Amino & Keto acid pair?
Name amino acid undergoing oxidative Deamination?
Name two transaminases of Diagnostic significance?
Importance of transamination?
Name enzymes of oxidative deamination.
Name two enzyme of nonoxidative deamination.

31. Fate of Ammonia & Urea
Cycle
Dr. Smita Pakhmode
NKP SIMS & RC, Nagpur

32. Ammonia is toxic
• It has to be detoxified
• Never transported in free form
• Low blood levels(15-45µgm/dl).

33. Overview of Ammonia Metabolism
Transaminatio &
Deamination of
Amino Acid
Catabolism
of
Nucleotide
Action of
Intestinal
Bacteria on
Urea
Glutamate
Glutamine
Urea
Liver
Catabolism
of biogenic
Amines
Glutamine ,
Alanine
&
Free NH3
15-45
µgm/dl
Liver, Brain & Intestine
Muscle
Excretion by
Kidney as Urea &
Ammonium Ions
Synthesis of NEAA
Synthesis of Purines/
Pyrimidines

34. Transport of Ammonia:
Formation of Glutamine
NH4 GI. Synthetase H2O
L-Glutamate Glutamine
ATP
Mg++
ADP + Pi
(Temp Storage)
H2O
Glutaminase
( Kidney, liver,Int. cells)
Urine NH4
1. Unidirectional
2. Requires ATP
3. Liver, intestine, Brain
4. Anaplerosis.
Major pathway for the disposal of ammonia in BRAIN
Glutamine formation depletes TCA cycle intermediate
Glutamate
Transaminidation reaction
Synthesis of purine &
Pyrimidine
Detoxification by
conjugation
Synthesis of Glutamate

35. Transport of Ammonia by muscle to liver by
Glucose Alanine Cycle

36. AMMONIA INTOXICATION:
α – keto glutarate Glutamate
H2O
NH3
NAD(P)
NAD(P)H + H+
Zn ++
Reversible Reaction
Mitochondion
1Utilization of α – keto glutarate slows TCA cycle, Leads to depletion of
energy (ATP)
2. Deficiency Of GABA ( inhibitory NT) in brain
3. Increase entrance of tryptophan in brain ( in exchange of glutamine)
…. ↑ stimulatory NT
4. Incresed synthesis of toxic alpha keto glutaramate
GDH
Ammonia toxicity: Nausea , vomiting, Blurring of Vision , slurring speech and
flapping tremors…………….. Hepatic Coma

37. Functions of Ammonia:
synthesis of
• Urea
• purines & Pyrimidine
• Non essential Amino Acid
• Aspargine & Amino sugar
Ammonium Ions are utilized for acid base regulation
Disposal of Ammonia in different organism:
Amniotelic: aquatic Animals excretes Ammonia
Uricotelic: Birds & Reptile excretes as uric Acid
Ureotelic: Mammals including In Humans excretes as Urea

38. Urea Cycle(Krebs-Henseleit cycle)
• Major route of detoxification of Ammonia
• Occurs in Liver
• First two steps occurs in mitochondrion & remaining
in the cytosole.
• First elucidation by Krebs & Kurts-Henseleit Cycle in
1932

39. Co2+ NH3
NAG.
2ATP
2ADP +
Pi Carbamoyl
Phosphate
Citrulline
Argino
succinate
Arginine
Ornithine
ATP
AMP + PPI
H2O
Ornithine
Transcarbomoylase
Carbomoyl Phosphate
Synthase 1
Arginosuccinase
synthase.
Arginosuccinase
Arginase
Mitochondrion
Cytosol
H2O
UREA CYCLE
Malate
OAA
Fumarate
Aspartate

40. Excreted in Kidney
• Urea Urease
Intestine CO2 + NH3
Faeces Blood
5 Enzymes involved
Amino Acid…. 6 2 Protein
3 NPN Ornithin, Citrullin,
Arginosuccinic Acid
Activator- N Acetyl Glutamine

41. Energetics:
4 Phosphate bond (ATP )used: 2 CPS1 & 2
ASS
2.5 ATP formed: Fumarate
Total Consumption: 1.5 ATP/Cycle.
Final Reaction:

42. Regulation of urea cycle
Synthesis of NAG
CPS I
Regulatory Enzyme
Arginine, Glutamin & High Protein Diet
Acetyl CoA Glutamate.
CoA. N Acetyl Glutamate
Acetate
NAG synthase NAG Hydrolase
Feed forward Regulation

43. Relation betweenTCA & Urea cycle
• Urea cycle TCA cycle
Fumarate formed Fumarate Malate OAA
Aspartate utilised OAA Aspartate
CO2 utilised CO2 is formed.
1.5 ATP utilised 10 ATP generated.
Urea Bicycle

44. Co2+ NH3
NAG.
2ATP
2ADP +
Pi Carbamoyl
Phosphate
Citrulline
Argino
succinate
Arginine
Ornithine
ATP
AMP + PPI
H2O
Ornithine
Transcarbomoylase
Carbomoyl Phosphate
Synthase 1
Arginosuccinase
synthase.
Arginosuccinase
Arginase
Mitochondrion
Cytosol
H2O
UREA CYCLE
Disorders
Fumara
te
Aspartate
Hyperammonemia I
Hyperammonemia II
Citrullinemia
Arginosuccinic acid urea
Hyperarginemia
Hyperprnithinemia
AR
Hyperammonemia,
encephalopathy and
respiratory alkalosis

45. Table 1. Molecular Genetics of Urea Cycle Disorders
Disease Name
Enzyme involved Symptoms
Hyperammonemia Type I
Carbamoylphosphate
synthetase I deficiency
↑ Level NH3; MR
Hyperammonemia Type II Ornithine
carbamoyltransferase
deficiency
↑ Level NH3 & Glutamin in
blood & urine Orotic Acid urea
Hyperornithenemia
Defective ornithin
transport protein
(HHH syndrome):
Hhyperornithenemia
Hyperammonemia,
homocitrulinurea
Citrulinemia I
Argininosuccinate
synthase
↑ Level NH3 & Citrullin in blood
& urine
Argininosuccinic
aciduria
Argininosuccinate
lyase
↑ Level Argininosuccinic
acid in blood & urine, Meta
Acidocis, trichorrhexix Nodosa
Hyperarginemia Arginase 1
↑ Level Arginine in CSF &
urine. Arginemia & Arginurea
Urea Cycle Disorders

46. Urea Cycle Disorders
- Deficiency of any enzyme of urea cycle
- S/o Ammonia intoxication, Encephaopathy & respiratory
alkalosis
- Pr. Induced vomiting, intermittent Ataxia, irritability,
lethargy, & MR.
Investigations:
Raised blood Ammonia levels
Raised Plasma Amino Acid levels
Raised urinary organic acid excretion
Blood pH, PCO2
Management:
- When ammonium ions are not converted into citrulline & AG, it
is converted in to Glycine & Glutamin
- Hence exploit Alternate pathways for Nitrogen Excretion
1.Sodium Benzoate + glycine = hippurate
2.Phenylbutyrate + glutamine = phenylacetylglytamine

47. • During urea cycle , two N2 atoms are
derived from which compound?
• Activity of urea cycle increases in
starvation as well as in high protein diet.
Explain.

48. Blood urea
• N- 10-40 mg/dl.
• 15-30 Gm/day.Excreted in Urine.
• Blood urea: Test for renal function.
• Uremia ↑Bl. Urea due to renal failure.
• Azotemia ↑Bl.urea or N2 metabolite irrespective of
associated renal disease.
• Causes :
• Prerenal: ↑ Pr. Breakdown.
Surgery, prolong fever, Thyrotoxicosis.
• Renal: AGN, CGN, Nephrosclerosis.
• Post renal: Obstruction in urinary trac.

49. Fate of Carbon skeleton

50. Catabolism &Functions of
Individual Amino Acids
Dr. Smita Pakhmode
NKP SIMS & RC, Nagpur
Glycine

51. G
L
Y
C
I
N
E
GLUTATHIONE
CREATINE
PURINE
HEME
SERINE
GLYCOCHOLIC ACID
GLYOXALIC ACID + NH3
HIPPURIC ACID
STIMULATES
GLUCONEOGENESIS
“PROTEIN EFFECT”
COLLAGEN
Formaldehyde Oxalate Malate
CREATININE
• Non essential ,
• Optically Inactive
• Glucogenic Amino Acid
• Synthesize many imp
compound

52. GLYCINURIA – Defect in renal absorption of glycine
GLYCINEMIA – Cause unknown. Early death
PRIMARY HYPEROXALURIA – increased urinary oxalate
Urolithiasis, Nephrolithiasis

53. Synthesis of Creatinine
• 3 AA---- Glycine, Arginine & Methionine.
• Synthesis:
Transamidinase(Kidney,pancreas)
Gly + Arginine Gaunidoacetic Acid
SAM
Methyl transferase(Liver)
SAH
Creatine
ATP
Creatin Kinase(muscle)
ADP + PI
Creatin Phosphate
Pi + H2O Nonenzymatic
Creatinine(excreted in urine)

54. Creatin
Synthesis of Creatinine

55. Sr. Creatinine
• N. Values:
Sr. Creatinine- 0.2 to 0.6 mg/dl.
Urine Creatinine – 1-2 Gm/day.
↑↑Values:
Physiologically- infants/ pregnancy.
Pathological:
Muscle diseases: Muscle dystrophies, fever, starvation, hyprthyroidism.
Kidney Diseases:UTI, Chronic nephritis, Renal failure.
Creatinine Clearance test:
Milligrams of creatinine cleared per ml of plasma.
Adv: More accurate , endogenously synthesized, does not changes with high diet.

56. Functions of Aromatic amino acid
Phenylalanine & Tyrosin
PHENYLALANINE
Essential amino acid.
Glucogenic & Ketogenic AA
Converted into Tyrosin.
Metabolised through Tyrosin
TYROSIN
Nonessential amino acid
Synthesized from PA
Glucogenic & Ketogenic AA
Melanin Dopamin Epinephrine
Nor
Epinephrine
Thyroid

57. Classical
Phenylketonuria
Atypical
Phenylketonuria

58. Tyrosine Catabolism:
(DHP
Acetate)
Cu2+
Phenylketoneuria
Tyrosinemia II
Neonatal
Tyrosinemia
Alkaptonuria

59. Tyrosine
Catabolism:
Tyrosine is ketogenic & Glucogenic Amino Acid
Tyrosinemia I

60. Disorders of Tyrosine Metabolism

61. Clinical Applications:
1. Cu2+ Deficiency
2. Malignant Melanoma
3. Leukoderma
4. Graying of Hair
5. Albinism
Cu2+
Tyrosinase
(Melanoblast)

62. Metanephrine VMA
MAO
COMT
• NT of Extrapyramidal tract
• Inhibit PRL synthesis
• Affects short & long tern
memory.(DARPP32)
• Def. leads to Parkinsonism
L DOPA is drug choice
for parkinsonism
Alpha Methyl DOPA:
Antihypertensive
↑ BP, Myocardial
Contractions
Relaxation of
smooth muscle
(bronchi)
Anti-insulin
Hormone of flight &
fight
↑Pheochromocytom
a & Neuroblastoma
Degradation
pathway:
Site: Adrenal Medulla &
Sympathetic Ganglion

63. Url for VMA estimation
abpedia.net/urine-24-hours-for-vma-
vanillylmandelic-acid-catecholamines-
24-hours-urine-neuroblastoma/

64. Synthesis of tyramine:
Tyr Tyramin (Vasoconstrictor)
Co2

65. Phenyl Alanine
Tyrosine
Phenylpyruvate
Phenyl lactate
Phenyl Acetate
DOPA
Nor
Epinephrine
DOPAMINE
Epinephrine
Dopaquinone
MELANINE
Thyroid
Hormones
Phenyl
Hydroxylase
Mousy odor of urine &
Body fluid
Demyelination of
Neurons
MENTAL
RETARDATION ALBINISM
PHENYL
KETONEUREA
RECAP: Functions & Disorder of Aromatic amino acid
Phenylalanine & Tyrosine
Increased Con pf Phenyl
Alanine & P. Ketones
Aceto acetic Acid &
Fumaric Acid

66. Autosomal Recessive condition.
Frequency 1: 10000 birth ( 1:1500)
Pathology: Deficiency of PA hydroxylase
Symptoms: Agitation, Hyperactivity, tremors & Convulsion
Hypopigmentation, Limb plasticity & severe mental retardation.
Mousy odor of urine & Body fluid
PHENYLKETONURIA

67. PHENYLKETONURIA
Type I – CLASSIC PHENYLKETONURIA
most common
DEFECT:
Phenyl alanine hydroxylase
Mental retardation:
due to impaired myelination in brain and nervous tissue, & ↓ NT,: low IQ,
convulsions
Mousy odour
•Increase in phenyl pyruvate, phenyl lactate, phenyl alanine in urine &
sweat:
•Hypopigmentation
•Impaired melanin synthesis: In adults: Seizures, psychoses, Eczema and
a peculiar odor
•Treatment:
• Low phenyl alanine diet
Hyper phenylalaninemia Type II and Type III – Defect in dihydrobiopterin
reductase
Hyper phenylalaninemia Type IV and V : defect in dihydrobiopterin
biosynthesis

68. Phenylketonuria:
• Tests of Detection:
1. Blood Phenyl alanine level: > 20 mg(N. level: 1-2
mg/dl)
2. Guthrie test:
3. Fecl3 test: (phenyl pyruvate)
4. DNA Probes:
5. Tandem Mass spectroscopy
6. Management:
7. Early detection is key (5Units IQ lost/10 weeks
delay)
8. Low Phenyl Alanine Diet ( Food based on
Topioca)
PKU Carrier state:
Heterozygous state
Responds to PA load test: 4gm PA/IV : Increases
levels in blood.

69. TYROSINEMIA TYPE I( Hepatorenal)
AR (1:1000)
Defect : FUMARYL ACETOACETATE HYDROLASE
Tyrosinemia type 1: Tyrosine is not cleaved and
leads to formation of toxins like fumarylacetoacetate,
Succinyl acetone and
amiolevulinic Acid.
This leads to kidney failure, liver failure and liver
cancer.
Acute Tyrosinosis – Infant exhibits diarrhea,
vomitting, cabbage like odour, Liver failure, cirrhosis
death if untreated
Chronic Tyrosinosis – Milder symptom, death by 10
years
Diagnosis: ↑ Tyrosin, ↑ Succinyl acetone, ↑ p HPPA in
urine
Treatment: Low tyrosine diet, low phenyl alanine diet
Tisinone (NTBC): P-HPP dioxygenase inhibitor

70. TYROSINEMIA TYPE II OR RICHNER
HANHART SYNDROME (oculocutaneous)
Defect : HEPATIC TYROSINE TRANSAMINASE
Plasma tyrosine increased
Eye – Skin lesions, moderate mental retardation.
SELF MUTILATION, painful coreal lesions &
photophobia
Urine: Increase phenyl pyruvate, lactate, n-acetyl
tyrosine and tyramine in urine
NEONATAL TYROSINEMIA
DEFECT: p HYDROXY PHENYL PYRUVATE HYDROXYLASE
Blood Tyrosine phenylalanine increased
Transient hypertyrosinemia of newborn
Vit C supplementation helps to overcome.
Urine tyrosine, p phenyl lactate, n acetyl tyrosine, tyramine increased
Treatment: Feeding diet low in protein

71. PHENYLALANINE
TYROSIN
Aceto acetic Acid &
Fumaric Acid
Homogentisic Acid
H. Acid Oxidase
Benzoquinone Acetate
Excretion of Alkapton
Black color to urine
Ochronosis
Alkaptonurea
P A Hydroxylase
Alkaptonuria
3rd or 4 th
decade of life
AR,
1:250000 births

72. ALKATONURIA
Historic interest since it formed the basis for
Noted in the 16 th century
DEFECT: HOMOGENTISIC ACID OXIDASE
Homogentisic acid accumulated in the urine which on standing in air is oxidized to
black pigment
Long standing disease
Black pigment deposited in sclera, ear, nose and other cartilages, connective tissue
OOCHRONOSIS and leads to ARTHRITIS
Ascorbic acid prevents oxidation of homogentisate and its deposition

73. • Diagnosis:
• Urine blacken on standing
• Urine FeCl3 test : Positive
• Benedicts test: Positive
Treatment:
No specific treatment available
Low PA diet (<500 mg/day)
recommonded

74. Albinism
• AR (1:20000)
• Deficiency of Tyrosinase(↓ Synth of Melanin)
• Symptoms: white skin, white hair & blue sclera
• Photophobia, nystagmus & ↓ visual acuity ,

75. Tryptophan (Trp)
• Most complex of all the amino acids.
• Essential amino acid.
• Contains Indol ring.
• Glucogenic and ketogenic AA.
• Four of its carbons yield acetoacetyl-CoA.

76. Tryptophan
Alanine
(Glu)
Formyl
Group
Excretory
Products
Acetoacyl CoA
( Keto)
OH -Indol
Acetic acid
INDICANS
Specialized Products
Catabolism
Products
Serotonin Melatonin
Neurotransmitters
Coenzyme
NAD/NADP

77. Metabolism of Tryptophan
99% 1%
Major catabolic Pathway
• Liver Target tissues
• Oxidation of tryptophan Converted to serotonin
• Synthesis of NADP & NAD Synthesis of melatonin by
• Transmethylation.
•
Kynurenin pathway Serotonin pathway

78. Tryptophan
N Formyl Kynurenine
Kynurenine
THAF
Formyl
THAF
3OH-Kynurenine
3OH-Hydroxy
Anthranilic Acid
NAD Pathway
Tryptophan
Pyrrolase(Fe)
(o2)
+Corticosteroid
1Carbon Pool
Alanine
Kynureninase, PLP
B6
Aceto Acetyl COA
↓B6 ↓B3
Pellagra
Xantheurenic Acid
Quinoline PRT Py PO4 deficiency
Kynurenine
Anthranilate Pathway
Glucogenic AA
Ketogenic AA
XANTHENURATE
Urine greenish yellow in def
XANTHURENIC ACIDURIA
60

79. Tryptophan
THBP
DHBP
NADP+
NADPH + H
Tyrp Hydroxylase
o2
H2 O
5 Hydroxy Tryptophan (5HT)
5 Hydroxy Tryptoptamine
(Serotonine)
PLP
Co2
Acetyl CoA
CoA
Acetyl
Serotonine
SAM
SAH
Acetylase
Methyl Transferase
Melatonin
O2
NH3
Hydroxy Indol Acetic Acid
MAO
Decarboxylase
Serotonine Pathway
Site:Brain
Mast cells,
GI track,
Platelets

80. • Serotonin (50-200ngm/ml):
• Neurotransmitter: Antidepressant
• Involved in the regulation of cerebral activity
• Controls behavioral patterns, sleep,BP& body temp.
• Decrease serotonine levels causes depression.
• Regulates GIT motility
Raised level
Carcinoid tumour:
Oat Cell tumour
Dermoid cyst
Medullary thyroid Carcinoma
Reduced Level:
Parkinsonism
Downs syndrome
Phenyl ketoneuria
Severe Depression
Carcinoid Syndrome: Argentaffinoma
Flushing, sweating & Intermittent Diarrhoea.
Pallegra : 60% channelization
Impairs synthesis of NAD/NADP
Negative N2 Balance.
MAO Inhibitors:
iproniazide
Tricyclic Antidepressant
SSRI

81. Food for thought
Why do we like
Chocolates??
Why do eating on
carbohydrate food induces
slip?

82. MELATONIN:
Synthesized from Pineal gland.
Formed by transmethylation of serotonin.
Involved in the circadian rhythm, diurnal variation.
Sleep wake cycle
Nocturnal rise opens the sleep gate.
Helps in reset of sleep pattern
↓production of MSH, ACTH.
↓effect on ovarian function.
Perform neurotransmitter function.
Why do we get sound
sleep in dark?

83. Hartnup’s Disease
• Hereditary AR disorder of
Tryptophan Metabolism
• Impairment of absorption &
transport of Trp & other neutral
Amino acid from intestine &
renal tubule.
• C/S: Rash, photosensitivity, MR,
Dermatitis, Ataxia.(Pellagra)
• Low plasma Tpt levels & other
amino acid
• Raised excretion of 5 Hydroxy
Indole Acetate( Obermeyers
test)

84. Histidine Metabolism
Semiessential AA
Strong buffer Pka
6.1
Heme- globin Histidine
Urocanic Acid
Immidazole Propionic Acid
Formino Glutamic Acid
Formino THF
NH3
Histidase
Uroconase
H2O
I P Hydrolase
H2O
Glutamic Acid
TH Formino
Transferase
Histidenemia: AR
↑ Histamin & Imm Pyruvate
M R, Delayed speech development
Urocanic Aciduria
Excretion in urine
Imm A A uria: AD
Cerebromacular & Retinal
degeneration
FA deficiency
↑ FIGLU
FIGLU excretion test +ve
Alpha KG Glucogenic

85. Histamine
Imidazole Acetic
Acid
Histaminase
MAO
Histidine
Decarboxylase
Mast cells,platelates &
Basophills
Act: Peripheral
Vasodilatation & Anaphylaxis
Anti histaminic Drugs:
Chlorphenarmine, certizine
Histamine Synthesis:
Histidine
Co2
NAD+
NADH
O2, H2 O
NH3, H2o2

86. Groups containing single carbon are formed from
several amino acid during their metabolism.
Different coenzyme transport them and donate to
the precursors to form different products.

87. Groups structure Carried by
Formyl -CHO N5-formyl THFA and N10-formyl-THFA
Forimmino -CH=NH N5-formino- THFA
Methenyl =CH- N5, N10 methenyl- THFA
Hydroxymethyl -CH2OH N10 hydroxymethyl- THFA
Methylene -CH2 N5, N10 methelene- THFA
Methyl -CH3 N5-methyl- THFA & Methyl
Cobalamin
One carbon compound which donates carbon units

88. Trptophan Formate N10-formyl-THFA
• Co2 + H2O
• C2-Purine
synthesis
• F-M-RNA
Histidine FIGLU N5 Formino
THF
N5, N10 Methenyl THFA
THF
THF
Serine
Glycine
THF
N5, N10 methylene- THFA
Pyrimidine
Synthesis
(TMP), Gly & Sr
Choline
Betaine N5-methyl- THFA
Synth. Of Met
from
Homocysteine
Methionine SAM Synth. Of cholin
creatinine,
Epinephrine,
tRNA,DNA
Precursors Carrier Derivatives
Utilization of 1C
compounds
Vit B12
Hydroxy
Methyl
THF Reductase
C8 Purine

89. G
L
Y
C
I
N
E
GLUTATHIONE
CREATINE
PURINE
HEME
SERINE
GLYCOCHOLIC ACID
GLYOXALIC ACID + NH3
HIPPURIC ACID
STIMULATES
GLUCONEOGENESIS
“PROTEIN EFFECT”
COLLAGEN
Formaldehyde Oxalate Malate
CREATININE
• Non essential ,
• Optically Inactive
• Glucogenic Amino Acid
• Synthesize many imp
compound

90. Role of Vit B12 in One Carbon
Metabolism
Folate
Cycle
Methionine
Cycle
Vit B12: transfer methyl group from formate cycle to Methionine
cycle
Coenzyme

91. Glycine
Serine
(NAD,
lipoamide)
Hydroxy Methyl Transferase
THF
N5-methyl- THFA
Threonine
Threonine Aldolase
+ NH4
Gly synthase
/ Gly Cleavage
Complex
methylene- THFA
THF
A. Methyl
transferase
Glycoxalate
Gly.
Amino
Transferase
Glutamate/
Alanine
Amino methyl
group
CO2 PLP,
Oxi.
deamination
Major route of
catabolism
Glucogenic
pathway
Pyruvate
Dehydratase
Non Ketotic Hyperglycinemia
Defect in Gly Cleavage system
↑ Gly in Blood, urine, CSF
Syp: Sever MR & Seizures
T/t: Genetic counselling
Glycolate Oxalic acid
Glycoxalate
Reductase
PRIMARY HYPEROXALURIA –
increased urinary oxalate
Urolithiasis, Nephrolithiasis
Synthesis of glycine: Degradation of glycine

92. PRIMARY HYPEROXALURIA – Type 1:
AR, Protein targeting defect
( abormal location of enzyme)
Enzyme: Alanine- Glycoxylate Amino Transferase
Block in the main pathway of synthesis of glycine
Raised level of Glycoxalate leads to more excretion of oxalate occurs
in urine
Renal: Urolithiasis, Nephrolithiasis, renal colic
Extra renal: heart ,blood vessels and bone oxalosis
PRIMARY HYPEROXALURIA – Type 2
Enzyme: cytoplasmic Glycoxylate Reductase
Less sever, causes urolithiasis
Management: increase water intake
less in Oxalate containing food
GLYCINURIA – Defect in renal absorption of glycine

93. Synthesis of Creatinine
• 3 AA---- Glycine, Arginine & Methionine.
• Synthesis:
Transamidinase(Kidney,pancreas)
Gly + Arginine Gaunidoacetic Acid
SAM
Methyl transferase(Liver)
SAH
Creatine
ATP
Creatin Kinase(muscle)
ADP + PI
Creatin Phosphate
Pi + H2O Nonenzymatic
Creatinine(excreted in urine)

94. Creatin
Synthesis of Creatinine

95. Sr. Creatinine
• N. Values:
Sr. Creatinine- 0.2 to 0.6 mg/dl.
Urine Creatinine – 1-2 Gm/day.
↑↑Values:
Physiologically- infants/ pregnancy.
Pathological:
Muscle diseases: Muscle dystrophies, fever, starvation, hyprthyroidism.
Kidney Diseases:UTI, Chronic nephritis, Renal failure.
Creatinine Clearance test:
Milligrams of creatinine cleared per ml of plasma.
Adv: More accurate , endogenously synthesized, does not changes with high diet.

96. METHIONINE
• S-containing, non essential amino acid.
Glycogenic AA.
• Functions:-
• Essential AA
• Forms various compounds with Transmethylation
( Creatine, Epinephrine, Choline ,Carnitine, DNA methylation)
• Initiates protein biosynthesis
• Conversion to cysteine & cystine
Metabolism of Methionine:
1 Activation of Methionine
2 Conversion of Methionine to Cysteine
3.Metabolism of cysteine

97. • FUNCTIONS OF SAM:-( Methyl transferase):-
• Irreversible transfer of methyl group
• Gaunido acetate ……………………… Creatine
• Norepinephrine ……………………… Epinephrine
• Ethanolamine ………………………. Cholin
• Acetyl serotonin ………………………. Melatonine
• Pre. AA ………………………. Pr. Methylated AA
TRANSMETHYLATION:-
Transfer of methyl group from active methionine to acceptor.
Methionine is activated to donate methyl group
L methionine S-Adenosyl S-Adenosyl
Methionine Homocysteine
L methyl adenosyl
transferase
ATP Pi + PPi
Precursor. Product
Methyltransferase

98. Metabolism of Methionine
L methyl adenosyl
transferase
ATP Pi + PPi Precursor.
Product
Methyltransferase
L methionine
Homocysteine
S-Adenosyl
Homocysteine
Adenosine
Adenosine
Homocysteinase
Homocysteine
Methyl Transferase
THF
N5-methyl-
THFA
B12
Cysteine
Syntheis
S-Adenosyl
Methionine
Homocystinuria Ty II
Substances formed by the
transmethylation reactions are:
1. Creatin
2. Betain
3. Cholin
4. Epinephrine
5. melatonine

99. Homocysteine Serine
Cystathionine
Homo Serine Cysteine
Cystathionine beta
synthase
Cystothioninase
PLP - H2O
+ H2O
⍺ Keto Hydroxy Butyrate
Propionyl Co A
NH3
CO 2 H2O
Succinyl
CoA
TCA
Cycle
Glucose
Homocystinuria Ty I
Symptoms: MR,
Charlie Chaplin gait,
skeletal deformities,
Ectopia Lentis,
Myopia, Glaucoma
Metabolism of Sulphur containing Amino Acid: Cysteine formation

100. Homocystinuria:
Cause: Accumulation of Homocysteine, AR
1:200000 births
Genetic Enzyme Def:
Cystathionine beta synthase
Homocysteine Methyl Transferase
Vit B12 deficiency
Acquired: Aged person, Vit B6,B12 Deficiency
Smoker, Alcoholics & Hypothyroidism
Pathophysiology:
↑↑ Homocysteine: LDL oxidation,
interferes with collagen cross linking
Atherogenic
↑↑ risk of Myocardial infarction
Maternal Hyperhomocysteinemia causes
Neural tube defect.
High dosage of folate are supplied in
pregnancy

101. Homocystinuria:
Diagnosis:
Blood: Raised plasma Homocysteine( 50-100times) & low Methionine
level
Urine: Homocysteine ( > 300 mg/24hr)
Cyanide Nitroprusside test: positive
The sodium cyanide–nitroprusside test is a rapid, simple, and qualitative
determination of cystine concentrations. Cyanide converts cystine to
cysteine. Nitroprusside then binds, causing a purple hue in 2-10
minutes.
Symptoms:
MR, Charlie Chaplin gait, skeletal
deformities, Ectopia Lentis, Myopia,
Glaucoma
Activation of Hegmen factor leads to
intravascular thrombosis

102. Metabolism of cysteine
cysteine
Pyruvate
Beta MercaptoPyruvate
Beta Mercapto
Ethanolamine
Coenzyme A
Gama
Glutamyl
Cysteine
Glutat
hione
PLP
Cystic Acid
Taurine
O2
CO2
Inhibitory
Neurotransmitter
Mediator of Ca2+ Influx
Active Sulphur doner
1.Synthesis of sulfatides
2.Sulfation GAG
3.Conjugation reaction in detoxification
PLP
TA
Cysteine
Sulphanilic Acid
Non enzymatic
desulfinase
Adenosine 5
PO4.
3phospho adenosine
5 phosphosulfate
(PAPS)
• Amino A transport
• Maintains RBC
memb integrity
• Acts as coenzyme
• Reduction of Met Hb
• Activation of enzyme

103. Cysteine
CYSTINURIA : Due to renal tubular defect cysteine in urine increases
20-30 times.
Cysteine is insoluble and hence PRECIPITATES in tubules forming
cystine calculi
Crystalluria, obstructive Uropathy,
T/t: Raise urinary volume by increasing fluid intake.
Na Bicarbonate: raised solubility of cystein
CYSTINOSIS : Familial, INHERITED. AR
Abnormality in the transport of cystine
----Widespread Deposition of calculi in many tissues including kidney,
liver , spleen & Bone marrow.
early death
T/t: Raise urinary volume by increasing fluid intake.
Na Bicarbonate: raised solubility of cysteine
D penicillamine

104. Branched Chain Amino Acid
Leucine, Isoleucine, Valine
Essential Amino acid
Keto,both , glucogenic
Utilized by muscles for energy
Acts as Fuel for brain in starvation

105. Valine Leucine Isoleucine
Corresponding Keto acids
⍺ Keto isovaleric acid. ⍺ Keto isocaproicacid ⍺ Keto beta methylvaleric acid.
Corresponding ⍺ β unsaturated acyl co A thioesterases
Methyl Acrylyl Co A. Methyl crotonyl Co A. Triglyl Co A
Glucose. Fat Glucose & Fat
Branched chain Amino
Acid Transaminase
⍺ Keto acid DH
NAD-CoASH
NADH Co A MSUD
Acyl COA DH
FAD
FADH2
Isovaleric Aciduria
Disorder of Valin
meta.
Chessy odour in
breath & body
Acidosis & MR

106. Symptoms: Convulsion, MR, vomiting ,
acidosis, coma, Death with 1year of life.
Urine: Maple syrup like smell
Presence of branched chain amino acid
Rothras test: +ve
Enzyme analysis of cells
Protein
(Dietary & Muscle proteins)
Branched chain
amino acid
⍺ Keto acid DH
Energy
Growth
Building up of
BCAAs & Other
substances
Acidosis & Mental
retardation
T/t:
Diet low in branched chain amino acid
High dosage of thiamine
Liver transplantation
Maple syrup urine disease
Diagnosis should be done 1
week prior to birth

107. Case studies
• Case Study 1: A 40-year old male has been having frequent bouts of flank pain for the past
3-4 years. It has been clinically identified as being due to renal calculi (stones). The
chemical analysis of the stones were carried out and it was found that they are
predominantly composed of oxalates. The urinary content of oxalates were also elevated
up to 180 mg/day (normal < 50 mg/day). Supplementation of vitamin – B6 did not alleviate
the symptoms.
• Que 1A: What is your probable diagnosis ?
• Primary(Endogeneous) Hypoxalurea
• 1B: What is the this genetic defect?
• Deficiency of Enzyme Glycine Transaminase which blocks the conversion of Glycoxylate to
formate & Glycine. There is defect in prtein targeting because of which glycine
transaminase is present in the mitochondrion rather than in the peroxisomes. It leads to
accumulation of oxalate in all tissues.
• 1C: What is the role of vit B6in above disorder?
• Deficiency of vit B6 also leads to oxaluria but it responds to administration of Vit B6. But in
endogenous Hypoxalurea symptoms do not alleviate by administration of vit B6. Hence
this is to rule out Vit B6 deficiency as a differential diagnosis.
• 1D: How you can confirm the diagnosis?
• Estimation of blood oxalate, Urinary Oxalate, Urine Routine with microscopy. USG, Liver
Biopsy: Deficiency of Glycine transaminase

108. • Case Study 2: A 3-week old infant was passing urine which smelled like
burnt sugar. Subsequently, an overwhelming acidosis developed associated
with vomiting and CNS- related symptoms. On investigation, the
concentrations of branched chain amino acids (val, leu, and lle) in plasma
and urine were found to be very high.
• What is your diagnosis?
• Maple syrup urine disease.
• What is the enzyme defect for this disorder?
• Deficiency of branched chain alpha keto dehydrogenase.
• What is the cause of Mental Retardation in this disease?
• All branched chain amino acids are ketogenic. They acts as a alternate fuel
for brain in case of starvation. Because of deficiency of enzyme , they can
not be catabolized in the brain . Hence leads to mental retardation.
What is the cause of Acidosis in this disease?
Deficiency of branched chain alpha keto dehydrogenase leads to
accumulation of corresponding keto acids in the blood leading to
acidocis.
Suggest line of management in this disorder?
• Diet with low quantity of branched chain amino Acid. Mild variant will
respond to the high dosage of Thiamine. Liver transplantation is last
remeady .
•

109. Case Study 3: A 22-year old male is brought to the hospital with a
complaint of hematuria and severe pain in his lower right flank.
Urine examination revealed elevated levels of cystine, ornithine,
arginine and lysine. Microscopic examination showed hexagonal
crystal deposit. Urine exam was positive for the cyanide
nitroprusside test. Further, X-rays showed the presence of
stones in the kidney.
3A)What is your probable diagnosis?
probable diagnosis: Cystinurea
3B)What is the cause for this disorder?
Defect in transport system for absorption of amino acids like
cystine, ornithine, arginine and lysine. Cystine is relatively
insoluble hence has a tendency to precipitate forming stones in
the kidney & urinary tract.
3C) how this can be treated?
Drinking large quantities of water and alkalisisng the urine by
administering sodium bicarbonate. Restrict dietary intake of
cystine.

110. Case Study 4: A 5-year old girl was brought to the hospital with
vision problems and stunted growth. Her mother indicated that the
girl’s milestones were delayed and there were signs of mental
retardation. Clinical examination revealed that she had long thin
bones and the X-rays indicated signs of osteoporosis. Urine cyanide
nitroprusside test was positive. Vitamin B6 supplementation did not
result in any improvement.
4a)What is your inference about this case?
Homocysteinurea
4b)What is the possible cause of this disorder?
Deficiency of enzyme cystothionine synthase blocks conversion of
Homocystein in to cystothionine. Hence Homocystine accumulates
in the body. Skeletal deformities and MR is also associated with the
disorder. Homocystein extreted in the urine.
4c) what is significance of urine Cynide Nitroprusside test?
Cynide test is done for the presence of homocysteine in urine. The
magenta red coloured appearing in urine gives positive test.

112. TA/oxidative
decarboxylat
ion/ FAD DH
Symptoms:
Convulsion,
MR, vomiting ,
acidosis, coma
Urine: Maple
syrup like smell
Presence of
branched chain
amino acid
Rothras test:
+ve
Metabolism of branched chain Amino Acid

117. Catabolic Pathway of AA
• Amino Acid Keto Acid
Transamination
Keto Glutarate L Glutamate
Oxidative deamination
NH3 CO2
Urea
Urine

118. N acetyl glutamate
2 ATP
2 ADP
Leaves mitochondria
By translocase
ATP
AMP
MITOCHONDRIA
T
R
A
N
S
A
M
I
N
A
T
I
O
N

119. Urea cycle defects
• Hyperammonemia1 defect is X-linked (OTC) –
most common – the rest are autosomal
recessive
• Age of onset varies from 2 days to adulthood
• Severity varies from lethal hyperammonaemic
encephalopathy to asymptomatic
• incidence – estimated at around 1 in 8200
newborns

120. Clinical presentation
• Hyperammonaemia triggered by illness or stre
ss
• cyclical vomiting, lethargy, psychosis
• Encephalopathic (slow-wave) EEG pattern
• Brain atrophy on MRI after repeated episodes
• Chronic hepatic enlargement and elevation of
transaminases

121. Management
• Prevent protein catabolism – dextrose infusion,
limit protein intake
• Clear Ammonia – pump driven dialysis is fastest
• Exploit Alternate pathways for Nitrogen
Excretion
1.Sodium Benzoate + glycine = hippurate
2.Phenylbutyrate + glutamine =
phenylacetylglytamine

122. Treatment of deficiency of Urea Cycle enzymes
(depends on which enzyme is deficient):
 limiting protein intake to the amount barely
adequate to supply amino acids for growth,
while adding to the diet the a-keto acid analogs
of essential amino acids.
 Liver transplantation has also been used,
since liver is the organ that carries out Urea
Cycle.

125. • SEROTONIN:-
• Neurotransmitter…… control cerebral activity
• Vasoconstrictor
• Control behavioral pattern
• Regulates GIT motility
• In Brain:-
• Serotonine is synthesized in bound form.
•  Serotonine ……….. Depression
• Malignant Carcinoid Syndrome:-
• ↑ Proliferation of argentaffin cell
• ↑ Serotonin production & NAD / NADP production
• Symptoms:-
• ↑ Respiratory distress, ↑ BP, sweating
Functions of Serotonin

126. • One carbon Transfer: Transfer / exchange of one carbon
unit in biological reactions.
• one carbon unit takes part in the synthesis of different
compound
Role of THFA:
Produced from Folic acid
Tetrahydro Folic Acid acts as carrier
of one carbon molecule
N5 & N10 carries carbon units
ONE Carbon Metabolism

128. Groups structure Carried by
Formyl -CHO N5-formyl THFA and N10-formyl-THFA
Forimmino -CH=NH N5-formino- THFA
Methenyl =CH- N5, N10 methenyl- THFA
Hydroxymethyl -CH2OH N10 hydroxymethyl- THFA
Methylene -CH2 N5, N10 methelene- THFA
Methyl -CH3 N5-methyl- THFA & Methyl
Cobalamin
One carbon compound which donates carbon units

129. Generation of one carbon
groups
• Serine → Glycine: Methylene THF
(Serine hydroxymethyl transferase)
• Glycine cleavage system: Methylene
Histidine → FIGLU → N5 Formino THFA
• Tryptophan: Formyl THFA
• Choline & Betain: Donor of Hydroxy
Methyl group.

130. Interconversion
of one carbon
compounds

131. One carbon
generation &
utilization

132. One carbon units are
transported with
derivatives of
Tetrahydrofolates
One Carbon Pool: Pool
formed by different
one carbon units
TH4 derivatives donates its
carbon unit to the
precursor to form different
compounds with
regeneration of TH4
Role of FH4 in One Carbon transfer

133. Transfer of methyl group & Co2 groups:
Transfer of Carboxyl
group by Biotin..
Snthesis of Fatty
acids, Amino Acids &
Gluconeogenesis
Transfer of methyl
group by Methionine
_choline, Carnitin,
creatin, Epinephrine,
t RNA, t DNA