Proteins are composed of amino acids linked together by peptide bonds. There are 20 standard amino acids, of which 9 are essential and must be obtained through diet. Amino acids combine to form polypeptides and proteins, which take on unique 3D structures that determine their specific functions. Protein digestion breaks down proteins into amino acids so they can be absorbed and used for various purposes throughout the body.

1. Dr.Mahr-un -nisa
Proteins

2. Proteins-----AA
 Proteins are made from 20 different amino acids,
9 of which are essential.
 Each amino acid has an amino group, an acid
group, a hydrogen atom, and a side group.
 It is the side group that makes each amino acid
unique.
 The sequence of amino acids in each protein
determines its unique shape and function.

4.  Amino Acids
 Have unique side groups that result in
differences in the size, shape and electrical
charge of an amino acid
 Nonessential amino acids, also called
dispensable amino acids, are ones the body can
create.

Nonessential amino acids include alanine, arginine,
asparagines, aspartic acid, cysteine, glutamic acid,
glutamine, glycine, proline, serine, and tyrosine.

6.  Amino Acids
 Essential amino acids, also called indispensable
amino acids, must be supplied by the foods people
consume.

Essential amino acids include histidine, isoleucine,
leucine, lysine, methionine, phenyalanine, threonine,
tryptophan, and valine.
 Conditionally essential amino acids refer to amino
acids that are normally nonessential but essential
under certain conditions.

7. Amino Acid Requirements of Humans
--------------------------------------------------------------------
Nutritionally Essential Nutritionally Nonessential
--------------------------------------------------------------------
Argininea
Alanine
Histidine Asparagine
Isoleucine Aspartate
Leucine Cysteine
Lysine Glutamate
Methionine Glutamine
Phenylalanine Glycine
Threonine Proline
Tryptophan Serine
Valine Tyrosine
---------------------------------------------------------------------
a “
Nutritionally semiessential.” Synthesized at rates
inadequate to support growth of children.

8. What is protein
 Proteins
 Amino acid chains are linked by peptide bonds in
condensation reactions.

Dipeptides have two amino acids bonded together.

Tripeptides have three amino acids bonded together.

Polypeptides have more than two amino acids bonded
together.
 Amino acid sequences are all different, which
allows for a wide variety of possible sequences.

9. M. Zaharna Clini.
Chem. 2009
Peptide bond

10. The Chemist’s View of
Proteins
 Proteins
 Protein Shapes

Hydrophilic side groups are attracted to water.

Hydrophobic side groups repel water.

Coiled and twisted chains help to provide
stability.

11. M. Zaharna Clini.
Chem. 2009
Classification of protein
 Proteins are polymers of amino acids produced
by living cells in all forms of life.
 A large number of proteins exist with diverse
functions, sizes, shapes and structures but each
is composed of essential and non-essential
amino acids in varying numbers and sequences.
 The number of distinct proteins within one cell is
estimated at 3,000 - 5,000
 The most abundant organic molecule in cells (50-70%
of cell dry weight)

12. M. Zaharna Clini.
Chem. 2009
Size
 A typical protein contains 200-300
amino acids, but some are much
smaller and some are much larger
 Proteins range in molecular weight from
6,000 Daltons (insulin) to millions of
Daltons (structural proteins)

13. M. Zaharna Clini.
Chem. 2009
Protein Structure
 Primary structure –
sequence of AA
 In order to function properly,
proteins must have the correct
sequence of amino acids.
 e.g when valine is substituted
for glutamic acid in the β chain
of HbA, HbS is formed, which
results in sickle-cell anemia.

14. M. Zaharna Clini.
Chem. 2009
Secondary structure
 Initial helical folding
 Beta pleated sheet
 Held together by
Hydrogen bonding

15. M. Zaharna Clini. Chem. 2009
Tertiary Structure
 Chain folds back on itself
to form 3D structure
 Interaction of R groups
 Responsible for biologic
activity of molecule

16. M. Zaharna Clini. Chem. 2009
Quaternary structure
 2 or more polypeptide chains
binding together
 eg. Hemoglobin
 Hemoglobin has 4 subunits
 Two α chains
 Two β chains
 Many enzymes have
quaternary structures

17. M. Zaharna Clini.
Chem. 2009
Classification by Protein
Structure
 Simple Proteins (contain only amino
acids) are classified by shape as –
 Globular proteins: compact, tightly
folded and coiled chains

Majority of serum proteins are globular
 Fibrous proteins: elongated, high
viscosity (hair, collagen)

18. M. Zaharna Clini.
Chem. 2009
Classification by Protein
Structure
 Conjugated proteins contain non-amino
acid groups
 Amino acid portion is called apoprotein and
non-amino acid portion is called the
prosthetic group
 It is the prothetic groups that define the
characteristics of these proteins.
 Name of the conjugated protein is derived
from the prosthetic group

19. M. Zaharna Clini.
Chem. 2009
Conjugated Proteins
Classification Prosthetic
group
Example
Lipoprotein Lipid HDL
Glycoprotein Carbohydrates Immunoglo-
bulins
Phosphoprotein Phosphate Casein of
milk

20. M. Zaharna Clini.
Chem. 2009
Functions of proteins
 Generally speaking, proteins do everything in the living cells
 Functional classification of plasma proteins is useful in
understanding the changes that occur in disease:
 Tissue nutrition
 Proteins of immune defense

Antibodies
 Acute phase proteins

Proteins associated with inflammation
 Transport proteins( albumin, transferrin)

Proteins used to bind and transport
 Hemostasis

Proteins involved in forming clots and acting very closely with
complement

21. M. Zaharna Clini.
Chem. 2009
Functions of proteins
 Regulatory

( receptors, hormones )
 Catalysis,

enzymes
 Osmotic force

Maintenance of water distribution between cells
and tissue and the vascular system of the body
 Acid-base balance

Participation as buffers to maintain pH
 Structural, contractile, fibrous and keratinous

22. Monogastric Protein Digestion
 Whole proteins are not absorbed
 Too large to pass through cell membranes
intact
 Digestive enzymes
 Hydrolyze peptide bonds
 Secreted as inactive pre-enzymes
 Prevents self-digestion
H3N+
C
H
C
R
O
N
H
C
H
C
O
R
N
H
C
H
C
R
O
O–

23. Monogastric Protein Digestion
 Initiated in stomach
 HCl from parietal cells

Stomach pH 1.6 to 3.2

Denatures 40
, 30
, and 20
structures
 Pepsinogen from chief cells

Cleaves at phenylalanine, tyrosine, tryptophan

Protein leaves stomach as mix of insoluble protein, soluble
protein, peptides and amino acids
Aromatic amino acids
Pepsinogen
HCl
Pepsin

24. Protein Digestion – Small Intestine
 Pancreatic enzymes secreted
 Trypsinogen
 Chymotrypsinogen
 Procarboxypeptidase
 Proelastase
 Collagenase
Zymogens

25. Monogastric Digestion –
Small Intestine
 Zymogens must be converted to active form
 Trypsinogen Trypsin

Endopeptidase
 Cleaves on carbonyl side of Lys & Arg
 Chymotrypsinogen Chymotrypsin

Endopeptidase
 Cleaves carboxy terminal Phe, Tyr and Trp
 Procarboxypeptidase Carboxypeptidase

Exopeptidase
 Removes carboxy terminal residues
Enteropeptidase/Trypsin
Trypsin
Trypsin

26. Protein Digestion
 Small intestine (brush border)
 Aminopeptidases

Cleave at N-terminal AA
 Dipeptidases

Cleave dipeptides
 Enterokinase (or enteropeptidase)

Trypsinogen → trypsin

Trypsin then activates all the other enzymes

27. Trypsin Inhibitors
 Small proteins or peptides
 Present in plants, organs, and fluids
 Soybeans, peas, beans, wheat
 Pancreas, colostrum
 Block digestion of specific proteins
 Inactivated by heat

28. Protein Digestion
 Proteins are broken down to
 Tripeptides
 Dipeptides
 Free amino acids

29. Free Amino Acid Absorption
 Free amino acids
 Carrier systems

Neutral AA

Basic AA

Acidic AA

Imino acids
 Entrance of some AA
is via active transport

Requires energy
Na+
Na+

30. Peptide Absorption
 Form in which the majority of
protein is absorbed
 More rapid than absorption
of free amino acids
 Active transport
 Energy required
 Metabolized into free amino
acids in enterocyte
 Only free amino acids
absorbed into blood

31. Absorption of Intact Proteins
 Newborns
 First 24 hours after birth
 Immunoglobulins

Passive immunity
 Adults
 Para cellular routes

Tight junctions between cells
 Intracellular routes

Endocytosis

Pinocytosis
 Of little nutritional significance...
 Affects health (allergies and passive immunity)

32. Protein Transport in the Blood
 Amino acids diffuse across the
basolateral membrane
 Enterocytes → portal blood → liver →
tissues
 Transported mostly as free amino acids
 Liver
 Breakdown of amino acids
 Synthesis of non-essential amino acids

33. Groff & Gropper, 2000
Overview of Protein Digestion and
Absorption in Monogastrics

34. OVERVIEW OF AMINO ACID METABOLISM
ENVIRONMENT ORGANISM
Ingested
protein
Bio-
synthesis
Protein
AMINO
ACIDS
Nitrogen
Carbon
skeletons
Urea
Degradatio
n
(required)
1
2 3
a
b
Purines
Pyrimidines
Porphyrins
c c
Used for
energy pyruvate
α-ketoglutarate
succinyl-CoA
fumarate
oxaloacetate
acetoacetate
acetyl CoA
(glucogenic)(ketogenic)

35. Amino Acid Catabolism
 Deamination of Amino Acids
removal of the a-amino acids
Oxidative Deamination
Non-oxidative Deamination
Transamination

36. TRANSAMINATION

37. The term amphibolic is used to describe a biochemical
pathway that involves both catabolism and anabolism

38. Reductive amination catalyzed by
glutamate dehydrogenase (this is physiological
important becouse high conc. Of NH4 ion are cytotoxic)

39. Glutamine synthesis is coupled to
hydrolysis of ATP

40. Pyruvate is an amphibolic intermediate
in synthesis of alanine

41. Glutamte dehydrogenase, glutamine synthetase and
aminotranferases play central roles in amino acid
biostynthsis
 The combined action of the above said
enzymes converts inorganic ammonium
ion in to the α-amino nitrogen of AA

42. Asparagine synthesis is energetically
favorable due to coupling to ATP
hydrolysis

43. Serine biosynthesis(oxidation of the α-hydroxyl
group of the glycolytic intermidiate 3-phosphoglycerate by 3-
phosphoglycerate dehygrogenase convert it to 3-
phosphohydroxypuruvate. Transamination and subsequent
dephosphorylation is strongly favored)

44. Multistep pathway for glycine biosynthesis

45. Glycine is also synthesized from serine

46. Cysteine is
not
nutritionally
essential,
however it
is derived
from
methionine
+NH3
CH
C
H2
C
O-
O
H2
C S CH3

47. Tyrosine is
formed
from
phenylalanine

48. Hydroxyproline is formed after protein
synthesis

49. Selenocysteine is synthesized from
serine and selenophosphate

50. Amino acids that are synthesized de novo in humans.
All are related by a small number of steps to glycolysis
or TCA cycle intermediates.

51. Salvage pathways for formation of certain
nonessential amino acids from other amino acids
Amino Acid formed Precursor Amino Acid
Arginine Proline
Cysteine Methionine
Tyrosine Phenylalanine

52. NITROGEN BALANCE
Nitrogen balance = nitrogen ingested - nitrogen excreted
(primarily as protein) (primarily as urea)
Nitrogen balance = 0 (nitrogen equilibrium)
protein synthesis = protein degradation
Positive nitrogen balance
protein synthesis > protein degradation
Negative nitrogen balance
protein synthesis < protein degradation

53. UREA CYCLE
mitochondria
cytosol
Function: detoxification of ammonia
(prevents hyperammonemia)

54. FATE OF THE CARBON
SKELETONS
Carbon skeletons are used for
energy.
Glucogenic: TCA cycle
intermediates(gluconeogensis)
Ketogenic: acetyl CoA, acetoacetyl
CoA, or acetoacetate

56. Protein synthesis
 On-going, semicontinuous activity in all
cells but rate varies greatly between
tissues

57. Rate of protein synthesis
Ks (%/d)
Tissue Pig Steer
Liver
Gut
Muscle
23
45
5
21
39
2
Ks = fraction of tissue protein synthesized per
day

58. Protein synthesis
 On-going, semicontinuous activity in all cells
but rate varies greatly between tissues
 Rate is regulated by hormones and supply of
amino acids and energy
 Energetically expensive
 requires about 5 ATP per one peptide bond
 Accounts for about 20% of whole-body
energy expenditure

59. Protein degradation
 Also controlled by hormones and
energy status
 Method to assist in metabolic control
 turns off enzymes

60. Protein synthesis and
degradation
 Synthesis must exceed degradation for
net protein deposition or secretion
 Changes in deposition can be achieved
by different combinations of changes in
synthesis and degradation

61. Changes in deposition
Synthesis Degradation Deposition
No change
No change
No change

62. Protein synthesis and
degradation
 Synthesis must exceed degradation for
net protein deposition or secretion
 Changes in deposition can be achieved
by different combinations of changes in
synthesis and degradation
 Allows for fine control of protein
deposition

63. Proline biosynthesis(the initial reaction of proline biosynthsis converts the
ᵞ-carboxyl group of glutamate to the mixed acid anhydride of glutamate ᵞ-phospate.
Subsequent reduction form glutamate ᵞ- semialdehyde,, which following
spontaneously cyclization is reduced to L-Proline )

64. Protein synthesis and
degradation
 Other possible reasons for evolution of
protein turnover include
 Allows post-translational conversion of
inactive peptides to active forms (e.g.,
pepsinogen to pepsin)
 Minimizes possible negative consequences
of translation errors

65. Protein catabolism
 Some net catabolism of body proteins
occurs at all times
 Expressed as urinary nitrogen excretion

yields urea
 Minimal nitrogen excretion is termed
endogenous urinary nitrogen (EUN)

66. Urinary nitrogen excretion
Urine
KIDNEY
LIVER
Urea
Urea
CO2
Amino acids keto acids
NH3
Blood

67. Protein Synthesis

68. Protein Synthesis
 Synthesis= the process of building or
making
 DNA= (deoxyribonucleic acid) the
genetic code or instructions for the cell
 RNA= ribonucleic acid
 Amino Acids= building blocks of
proteins

69. DNA RNA
Deoxyribonucleic Acid Ribonucleic Acid
Sugar=deoxyribose Sugar= ribose
Contains 1 more H atom
than deoxyribose
Double stranded Single stranded- a single
strand of nucleotides
Nitrogen bases: ATCG Nitrogen bases: AUCG
U=Uracil

70. http://www.princeton.ed
u/
http://image
s2.clinicalto
ols.com/ima
ges/gene/dn
a_versus_rn
a_reversed.j
pg

71. STEP 1: TRANSCRIPTION= making
RNA
Location: Eukaryotes-nucleus
Prokaryotes-cytoplasm
 1. RNA polymerase binds to the gene’s
promoter
 2. The two DNA strands unwind and
separate.
 3. Complementary nucleotides are
added using the base pairing rules
EXCEPT:
 A=U


72. Try this example.
 Using the following DNA sequence,
what would be the complementary RNA
sequence?
 ATCCGTAATTATGGC
 UAGGCAUUAAUACCG

73. http://www.odec.ca/projects/2004/mcgo4s0/public_html/t3/mRNA%20to%20protein.gif

74.  1. Messenger RNA= mRNA is a form of
RNA that carries the instructions for making
the protein from a gene and delivers it to the
site of translation.
 Codon= three nucleotide sequence
 Transfer RNA= tRNA single strands of
RNA that temporarily carry a specific amino
acid on one end and has an anticodon
 Anticodon-a 3 nucleotide sequence that is
complementary to an mRNA codon
 Ribosomal RNA= rRNA- a part of the
structure of ribosomes

75. Codon and Anticodon
 Codon-found on mRNA Anticodon-found on tRNA
http://images.google.com/imgres?
imgurl=http://www.obgynacademy.com/basicsciences/feto
logy/genetics/images/codon_GCA.gif&imgrefurl=http://ww
w.obgynacademy.com/basicsciences/fetology/genetics/&u
sg=__4MvAO2N3sXbERXQwODVDSqtsOjM=&h=160&w=
168&sz=4&hl=en&start=5&tbnid=toyuIN8drVBr4M:&tbnh=
94&tbnw=99&prev=/images%3Fq%3Dcodon%26gbv
%3D2%26hl%3Den
http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleim
ages/kaiser/tRNA_arg.jpg

76. STEP 2-TRANSLATION-
Assembling proteins- in the
cytoplasm
 mRNA leaves nucleus and enters cytoplasm
 tRNA molecules with the complementary
anticodon and a specific amino acid arrives at
the ribosome where the mRNA is waiting.
 Peptide bond forms between amino acids
 tRNA molecule leaves and a new one comes
with another amino acid.
 Amino acids continue to attach together until
the stop codon and a protein is formed

77. SUMMARY
 Transcription= process of making RNA
from DNA
 Translation= RNA directions are used to
make a protein from amino acids
• DNA→RNA →Protein
 Transcription Translation
nucleus
Cytoplasm on
ribosome

78. DNA RNA
Deoxyribonucleic Acid Ribonucleic Acid
Sugar=deoxyribose Sugar= ribose
Contains 1 more H atom
than deoxyribose
Double stranded Single stranded- a single
strand of nucleotides
Nitrogen bases: ATCG Nitrogen bases: AUCG
U=Uracil

79. Video Clips
 http://www.youtube.com/watch?v=KvYEqG
 http://www.youtube.com/watch?v=B6O6uR

80. DNA Replication RNA Transcription
DNA polymerase is used. RNA polymerase is used.
DNA nucleotides are
linked.
RNA nucleotides are
linked.
A DNA molecule is
made.
An RNA molecule is
made.
Both DNA strands serve
as templates.
Only one part of one
strand of DNA ( a gene)
is used as a template.

81. Explain the steps in protein synthesis.
http://stemcells.nih.gov
/info/scireport/images/f
igurea6.jpg

82. Ruminant Protein Digestion
 Ruminants can exist with limited dietary
protein sources due to microbial protein
synthesis
 Essential amino acids synthesized
 Microbial protein is not sufficient during:
 Rapid growth
 High production

83. Protein in the Ruminant Diet
 Types of protein:
 Dietary protein – contains amino acids

Rumen Degradable Protein (RDP) – available for use by
rumen microbes

Rumen Undegradable Protein (RUP) – escapes rumen
fermentation; enters small intestine unaltered
 Varies with diet, feed processing
 Dietary non-protein nitrogen (NPN) – not true
protein; provides a source of nitrogen for microbial
protein synthesis

Relatively CHEAP - decreases cost of protein
supplementation

84. Ruminant Protein Feeding
 Feed the rumen microbes first (RDP)
 Two counteractive processes in rumen

Degradation of (dietary) protein

Synthesis of microbial protein
 Feed proteins that will escape fermentation to
meet remainder of animal’s protein requirements
 Escape protein, bypass protein, or
rumen undegradable protein (RUP)

Aldehydes increase inter-protein cross-linking

Heat treatment
 Utilization depends on

Digestibility of RUP source in the small intestine

Protein quality

85. Protein Degradation in Rumen
Feedstuff % Degraded
in 2 hours
Urea 100
Alfalfa (fresh) 90
Wheat Grain 78
Soybean Meal 65
Corn Grain 48
Blood Meal 18

86. Rumen Protein Utilization
 Factors affecting ruminal degradation
 Rate of passage

Rate of passage ↑ ⇒ degradation ↓
 Solubility in water

Must be solubilized prior to degradation
 Heat treatment

Degradation ↓
 N (and S) availability
 Energy availability (carbohydrates)

87. Protein Fractions
 Dietary proteins classified based on
solubility in the rumen
 A

NPN, instantly solubilized/degraded
 B1 B2 B3

Potentially degradable
 C

Insoluble, recovered in ADF, undegradable

88. Ruminant Protein Digestion
 Rumen microbes use dietary protein
 Creates difference between protein quality in feed
and protein actually absorbed by host
 Microbes break down dietary protein to
 Amino acids
 NH3, VFAs, and CO2
 Microbes re-synthesize amino acids
 Including all the essential amino acids from NH3 and
carbon skeletons
No absorption of protein or amino acids
from rumen (or from cecum or large
intestine!)

89. Protein Hydrolysis by
Rumen Microbes
 Process with multiple steps
 Insoluble protein is solubilized when possible
 Peptide bonds of solubilized protein are cleaved

Microbial endo- and exo-peptidases

Amino acids and peptides released
 Peptides and amino acids absorbed rapidly by
bacteria
 Bacteria degrade into ammonia N (NH3)
 NH3 used to produce microbial crude protein (MCP)

90. Microbial Crude Protein
(MCP)
 Protein produced by microbial synthesis in
the rumen
 Primary source of protein to the ruminant
animal
 Microbes combine ammonia nitrogen and
carbohydrate carbon skeleton to make
microbial crude protein
 Diet affects the amount of nitrogen
entering the small intestine as microbial
crude protein

91. Factors Limiting Microbial
Protein Synthesis
 Amount of energy
 ATP
 Available nitrogen
 NPN
 Degraded feed intake protein nitrogen (RDP)
 Available carbohydrates
 Carbon residues for backbone of new amino acid
Microbial crude protein synthesis relies on
synchronization of carbohydrate (for carbon
backbones) and nitrogen availability (for amino group)

92. Microbial Protein Synthesis
 Synchronization of carbohydrate and N availability
 NPN supplementation
 Carbohydrates used for carbon skeleton of amino acids
VFA (CHO fermentation)
Rumen NH3
Blood NH3
Adapted from Van Soest, 1994
Time post-feeding
Concentration
Carbon backbone
(from CHO fermentation)

93. Microbial Protein Formation
Dietary
NPN
Dietary
Soluble RDP
Microbial
Proteins
Amino Acids
Carbon Skeletons Sulfur Other Co-factors
NH3
ATP
Dietary
Starch Sugar
Dietary Cellulose
Hemicellulose
rapid slow
rapid
slower Dietary
Insoluble RDP
very
slow

94. Nitrogen Recycling
 Excess NH3 is absorbed
through the rumen wall to the blood
 Quickly converted to urea in the liver
 Excess NH3 may elevate blood pH
 Ammonia toxicity
 Costs energy
 Urea (two ammonia molecules linked together)

Relatively non-toxic

Excreted in urine

Returned to rumen via saliva (rumination important)
 Efficiency of nitrogen recycling decreases
with increasing nitrogen intake

95. Nitrogen Recycling
 Nitrogen is continually recycled to rumen for
reutilization
 Ability to survive on low nitrogen diets
 Up to 90% of plasma urea CAN be recycled to
rumen on low protein diet
 Over 75% of plasma urea will be excreted on high
protein diet
 Plasma urea enters rumen
 Saliva
 Diffuses through rumen wall from blood
Urea Ammonia + CO2
Urease

96. Feed Protein,
NPN and CHO
Feed
Protein
Feed NPN
NH3/NH4
Bacterial N
NH4
+
loss
MCP
RDP
RUP
Feed
Protein
AA
MCP AA
NH3
Liver
Blood Urea
Salivary N
ATP
RUMEN
SMALL INTESTINE

97. Ruminant Digestion and
Absorption
 Post-ruminal digestion and absorption
closely resembles the processes of
monogastric animals
 However, amino acid profile entering small
intestine different from dietary profile

98. Overview of Protein Feeding
Issues in Ruminants
 Rumen degradable protein (RDP)
 Low protein quality in feed ⇒ very good quality
microbial proteins
 Great protein quality in feed ⇒ very good quality
microbial proteins
 Feed the cheapest RDP source that is practical
regardless of quality
 Rumen undegradable protein (RUP)
 Not modified in rumen, so should be higher
quality protein as fed to animal

May cost more initially, but may be worth cost if
performance boosted enough

99. Salivary Urea
NPN
NH3
POOL
Dietary
Nitrogen Non-utilized Ammonia
NH3
UREA
LIVER
LEVEL TO
PROVIDE FOR
MAXIMUM
MICROBIAL GROWTH
MICROBIAL
PROTEIN
65% OF PROTEIN
35% OF PROTEIN
SMALL
INTESTINE
AMINO
ACIDS
AMINO
ACIDSPROTEIN
AMINO
ACIDS
PEPTIDES
Reticulo-rumen
RUP
RDP
Recycled urea

100. Functional Feeds
 Functional feeds may be defined as
any feed or feed ingredient that
produces a biological effect or health
benefit that is above and beyond the
nutritive value of that feedstuff
 Many feeds and their components fit
this definition

101. Functional Proteins
 Functional proteins are feed-derived
proteins that, in addition to their
nutritional value, produce a biological
effect in the body

102. Feedstuffs with Biologically
Active Proteins
 Milk
 Colostrum
 Whey Protein Concentrates/Isolates
 Plasma or serum
 Other animal-derived feedstuffs
 Fish meal
 Meat and bone meal
 Fermented animal-based products
 Yeast
 Lactobacillus organisms
 Soy products

103. Protein Size Affects Function
 Many protein hormones are functional even
when fed to animals
 thyrotropin-releasing hormone (TRH, a 3-amino acid
peptide)
 luteinizing hormone-releasing hormone (LHRH, a 10-amino
acid peptide)
 insulin (a 51-amino acid polypeptide)
 The smaller the peptide, the more “functional” it is
when fed
 100% activity for TRH, 50% for LHRH, and 30% for insulin
 Feedstuffs containing protein hormones (colostrum)
have biological activity when fed to animals

104. Production of Bioactive Peptides
From Biologically-Inactive Proteins
 Peptides produced from intact inactive
proteins by incomplete digestion via
proteases in stomach and duodenum or via
microbial proteases in rumen
 Many of these biologically active peptides
(typically 2-4 amino acid residues) are stable
from further digestion
 Some peptides bind to specific epithelial receptors
in intestinal lumen and induce physiological
reactions
 Some peptides are absorbed intact by a specific
peptide transporter system into the circulatory
system and transported to target organs

105. Responses to Feeding Functional
Proteins or Peptides
 Antimicrobial – including control of gut microflora
 Antiviral
 Binding of enterotoxins
 Anti-carcinogenic
 Immunomodulation
 Anti-oxidant effects
 Opioid effects
 Enhance tissue development or function
 Anti-inflammatory
 Appetite regulation
 Anti-hypertensive
 Anti-thrombic

106. Functional Activity of Major Milk Proteins
 Caseins (α, β and κ)
 Transport of minerals and trace elements (Ca, PO4, Fe, Zn, Cu), precursor
of bioactive peptides, immunomodulation (hydrolysates/peptides)
 β-Lactoglobulin
 Retinol carrier, binding fatty acids, potential antioxidant, precursor for
bioactive peptides
 α-Lactalbumin
 Lactose synthesis in mammary gland, Ca carrier, immunomodulation,
anticarcinogenic, precursor for bioactive peptides
 Immunoglobulins
 Specific immune protection (antibodies and complement system), G, M, A
potential precursor for bioactive peptides
 Glycomacropeptide
 Antiviral, antithrombotic, bifidogenic, gastric regulation
 Lactoferrin
 Antimicrobial, antioxidative, anticarcinogenic, anti-inflammatory,
immunomodulation, iron transport, cell growth regulation, precursor for
bioactive peptides
 Lactoperoxidase
 Antimicrobial, synergistic effect with Igs and LF
 Lysozyme
 Antimicrobial, synergistic effect with Igs and LF
 Serum albumin
 Precursor for bioactive peptides
 Proteose peptones
 Potential mineral carrier

107. Functional Activity of Minor Milk
Proteins
 Growth factors (IgF, TGF, EGF)
 stimulation of cell proliferation and differentation
 Cytokines
 regulation of immune system (interferons, interleukins,
TGFβ, TNFα)

Inflammation

Increases immune response
 Milk basic protein (MBP)
 Promotion of bone formation and suppression of bone
resorption
 Osteopontin
 Modulation of trophoblastic cell migration

108. Protein Fragments That Have
Biological Activity

109. Functional Protein Effects During
Toxin or Disease Challenge
 During intestinal inflammation, some functional proteins:
 Reduce

local inflammatory response

excessive activation of inflammatory cells

permeability
 Increase

Nutrient absorption

Barrier function

Intestinal health
 During intestinal inflammation, some functional proteins:
 Are absorbed and create adverse allergenic and immune
responses in the body
Modified from Campbell, 2007