Haemoglobin and jaunidice

1. Dr. Viyatprajna
Acharya

2. Heme is the
prosthetic group
of hemoglobin,
myoglobin, &
cytochromes.
Heme is an
asymmetric
molecule. E.g.,
note the positions
of methyl side
chains around the
ring system.
N
N
N
N
CH3 HC
CH3
S CH2
CH3
CH S CH2
CH3
CH2
CH2
COO
CH3
H3C
CH2CH2

OOC
protein
protein
Fe
Heme c

3.  Almost all cells
 Synthesised in normoblasts but not in RBCs
 Partly cytoplasmic, partly mitochondrial

5. Heme synthesis begins with condensation of glycine &
succinyl-CoA, with decarboxylation, to form d-
aminolevulinic acid (ALA).

OOC CH2 CH2 C S-CoA
O
+ 
OOC CH2 NH3
+

OOC CH2 CH2 C
O
CH2 NH3
+
CO2CoA-SH
H+succinyl-CoA glycine
d-aminolevulinate (ALA)
d-Aminolevulinic
Acid Synthase
PLP

6. ALA Synthase is the committed step of the heme
synthesis pathway, & is usually rate-limiting for the
overall pathway.
Located in mitochondria

7. PBG Synthase
(Porphobilinogen
Synthase), also
called ALA
Dehydratase,
catalyzes
condensation of
two molecules of
d-aminolevulinate
to form the pyrrole
ring of
porphobilinogen
(PBG).
C
C
N
H
CH
C
CH2
COO
CH2
CH2
COO
H2C
NH3
+
CH2
CH2
COO
C
CH2
O
NH3
+
CH2
CH2
COO
C
CH2
O
NH3
+
+
porphobilinogen
(PBG)
2 d-aminolevulinate
(ALA)
2 H2O
PBG Synthase

8.  Located in cytoplasm
 Enzyme contains Zn-- inhibited by lead
 Schiff base linkages are formed with Lys
residues of ALA and the enzyme
 Pyrrole rings are formed

9.  Condensation of 4 molecules of PBG
↓
Hydroxymethylbilane (HMB)
↓
Uroporphyrinogen III
(1st porphyrin of the pathway)
↓
Coproporphyrinogen III
PBG Deaminase
Uroporphyrinogen III synthase
UPG III decarboxylase
4 NH3
4 CO2

10. HO
NH
CH2
CH2
COO-
CH2
-
OOC
HN
CH2
COO-
CH2 CH2
HN
CH2
CH2
COO-
CH2 COO-
NH
CH2
COO-
CH2
CH2
COO-
COO-
hydroxymethylbilane

11. Coproporphyrinogen III
↓
Protoporphyrinogen III
↓
Protoporphyrinogen IX
↓
Heme (released to
cytoplasm)
CPG III oxidase
PPG III oxidase
Ferrochelatase/ Heme synthaseFe ++

12. 1. ALA synthase – regulated by heme; heme
acts as a co-repressor
2. ALA synthase – allosterically inhibited by
hematin.
when excess heme– Fe2+ is converted to Fe3+
(hematin)
3. Compartmentalization of the enzymes
4. Barbiturates – induce heme synthesis;
Cytp450 used for heme production

13. 5. ALA dehydratase & Ferrochelatase –
inhibited by Zn
6. INH – decreases availability of PLP
(Pyridoxal phosphate) – affects 1st step
7. ↑glucose – prevents induction of ALA
synthase

14. BREAK

15.  Porphyrias are genetic diseases
in which activity of one of the
enzymes involved in heme
synthesis is decreased (e.g., PBG
Synthase, Porphobilinogen
Deaminase, etc…).
Symptoms vary depending on
 the enzyme
 the severity of the deficiency
 whether heme synthesis is affected
primarily in liver or in developing
erythrocytes.
Porphyria = purple

17.  Either genetic (autosomal dominant or autosomal recessive) or
acquired. Heterozygotes are asymptomatic in between acute
attacks.
 Classified depending on site of overproduction and accumulation
of porphyrin, overlapping features common
Hepatic Erythropoietic
• Neurologic, mental
disturbances
• Abdominal pain
• Extremity pain, paresthesias
• Motor neuropathy
• Cutaneous photosensitivity –
long wave UV light excites
porphyrins in skins causing cell
damage
• Hemolytic anemia

18. • Autonomic Nervous System
• Peripheral Nervous System
• Hypothalamus
• Limbic area
Porphyrins excreted from liver
ALA crosses BBB 
Causes oxidative
damage
Accumulates in brain
with neuronal and glial
cell damage
Symptoms due to porphyrin
Precursor accumulation
Rather than deficiency of
Heme
Porphyrins don’t
Cross BBB
ALA induces liver
Damage via oxidative
effects

20.  Autosomal dominant
 PBG-deaminase is deficient
 Secondary increase in activity of ALA synthase
 ↑ ALA & PBG in blood and urine
 Present with “acute abdomen”
 Another group may have neurological
manifestations– sensory and motor disturbances,
confusion and agitation

21.  Most common porphyria which causes
skin manifestations
 Deficiency of hepatic UPG-decarboxylase
 Cutaneous photosensitivity  fluid filled
vesicles on sun exposed areas, friable skin,
wounds heal slowly, risk for infection, may
see hypertrichosis and hyperpigmentation
on face
 No neurologic manifestations
 Higher incidence of HCV and
hepatocellular carcinoma
 Precipitants frequently include alcohol,
estrogen and iron

22.  Avoid sunlight, use sunscreen
 Chloroquine or Hydroxychloroquine – form
complexes with porphyrins which enhance
excretion
 Repeated phlebotomy – goal Hct < 35% and
ferritin < 10 ng/ml. Usually requires removal of
12-16 units of blood.
 Charcoal
 Cholestyramine
 Beta carotene may increase tolerance of
sunlight throughVitamin A.

23.  Lead poisoning, ethanol- PBG synthase
 Malignancies – HMB synthase inhibited
 CRF, some cancers – UPG
decarboxylase
 Liver disease, some Ca, Benzene,
Arsenic, Mercury poisoning – CPG
oxidase
 Iron deficiency anemia, lead, anemia -
Ferrochelatase

24. The human race has one really effective
weapon, and that is laughter. Mark Twain

25.  Humans- 250-400 mg bilirubin produced
everyday (80% from Hb and 20% from
other heme-containing proteins e.g. Cyt,
myoglobin )
 Senescent RBC rupture (80%), premature
erythroid cell damage in BM (10%),
Myoglobin and Cytochrome damage
(10%) – pool of heme
 1g Hb = 35 mg bilirubin

26. Hemoglobin
Heme
Globin
Microsomal heme oxygenase
system
CO
3O2 + 5 NADPH
Biliverdin
Bilirubin
Biliverdin reductase
NADPH + H+
NADP+
This process takes place in RE system (Liver and spleen) and
bilirubin produced is water insoluble.

27. Biliverdin

28. ALB= Albumin, BT- Bilirubin transporter, GST = glutathione-S-
transferase, BMG= bilirubin monoglucuronide, BDG = bilirubin
diglucuronide

29.  Bilirubin binds to albumin- travel to hepatocytes
 Albumin is left, BT (Bilirubin transporter) carries
UCB into the hepatocytes
 Ligandin / ProteinY / glutathione-S- transferase
– binds to UCB and prevents its efflux
 Conjugation with Glucuronic acid with the help of
bilirubin Uridine diphosphate glucuronyl
transferase - BMG= bilirubin monoglucuronide,
BDG = bilirubin diglucuronide

30.  Conjugated bilirubin poured into 2nd part of
duodenum through bile
 Unchanged through proximal intestine
 Distal ileum & Colon- deconjugated by bacteria
 reduced to urobilinogen
 Urobilinogen further reduced
Setrcobilinogen & Mesobilinogen

31.  80% of these excreted either unchanged or
converted to urobilins , stercobilins
Feces, urine (impart colour)
 20% of these – enterohepatic circulation
 A small fraction (< 3 mg/ dl) – in urine
 If bacterial flora reduced, bilirubin is not
converted to urobilinogen instead re-oxidized to
Biliverdin → green stool

32.  In the absence of bilirubin
glucuronidation a fraction of bilirubin
is excreted as hydroxylated products –
may be by Microsomal P450 system or
mitochondrial bilirubin oxidase system
in liver and other tissues

33.  Normal level of Serum bilirubin- 0.2-1.0
mg /dl
 80% UC bilirubin – 0.2-0.8 mg/dl
 20% C bilirubin – 0- 0.2 mg/dl
 Latent jaundice – 1-2 mg/dl
 Jaundice - > 2 mg / dl

34.  Overproduction by
reticuloendothelial system
 Failure of hepatocyte uptake
 Failure to conjugate or excrete
 Obstruction of biliary excretion
into intestine

35. Inherited hyperbilirubinemia
Acquired hyperbilirubinemia

36.  Crigler- Najjar’s syndrome –
i)Type I – complete absence of glucuronyl
transferase
ii)Type II – partial absence of glucuronyl
transferase
 Gilbert’s syndrome- impaired hepatic intake &
↓conjugation
 Dubin - Johnson’s syndrome- defective excretion
of conjugated bilirubin; black pigmentation
 Rotor syndrome- defective excretion of
conjugated bilirubin; no pigmentation

37. 1. Pre-hepatic /
Haemolytic jaundice
2. Hepatocellular /
Hepatic jaundice
3. Obstructive jaundice
4. Physiological
jaundice of the
newborn

38. A. Hemolytic disease of the newborn
 Rh incompatibility
 Erythroblastosis fetalis
B. Hemolytic disease due to other causes
Congenital spherocytosis
G-6-PD deficiency
Incompatible blood transfusion
Hereditary spherocytosis

39.  Mild jaundice
 Maximum unconjugated bilirubin
 Urobilinogen +++ in urine and stool
 Urine colour is normal- absence of
bilirubin
 ↑ AST & ALT; ALP normal

40.  Viral hepatitis
 Toxic chemicals – alcohol,
chloroform, CCl4
 Drugs
 Cirrhosis

41.  UC &C bilirubin both are present
 ↓ urobilinogen in urine and feces
 Bilirubin in urine +
 Biphasic reaction inVan den Bergh
reaction
 ↑ALT, AST; ALP moderately high
 Cirrhosis will give a picture of both
hepatocellular as well as post-
hepatic jaundice

42.  Cholestasis- stagnation of bile
Intrahepatic cholestasis-
1. Chronic active hepatitis
2. Biliary cirrhosis
3. Lymphomas
4. Primary hepatoma
5. Obstructive stage of viral hepatitis
Extrahepatic cholestasis- stones, stricture in CBD,
CA head of pancreas, enlarged LN at porta hepatis

43.  Regurgitation of bile → biliary canaliculi
damage → infiltrate to lymph → blood
circulation
 ↑ Conjugated bilirubin in blood
 UBG is decreased ; in complete obstruction
it’s absent
 Clay coloured stool
 Bile salts in urine

44. After 2nd day of life jaundice
appears
Mild jaundice
Due to accelerated RBC
hemolysis
Immature hepatic system →
conjugation of bilirubin fails
Unconjugated hyperbilirubinemia
Hardly crosses > 15 mg/ dl
Disappears by 2nd wk of life

45. Pre-hepatic /
hemolytic jaundice
Hepatic /
Hepatocellular
Post-hepatic /
Obstructive
Aetiology Excessive
hemolysis
Parenchymal
disease
Obstruction to
biliary passage
Degree of
jaundice
Low Mod. to severe Mod. to severe
Feces Dark Pale Clay
Van den Bergh
reaction
Indirect Biphasic Direct
Pigment in
circulation
UC Bilirubin C & UC C
Bilirubin in urine nil + ++
Urobilinogen in
urine
++ + or ± ↓ or absent
Fecal
Setrcobilinogen
↑↑ ↓ ↓ or absent
Steatorrhoea ─ + ++

46. Hard work is a substitute to good luck