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Dr.Mahr-un -nisa
Proteins
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.
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.
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.
A m in o A c id R e q u ir e m e n t s o f H u m a n s - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - N u t r i t io n a l ly E s s e n t ia l N u t r i t io n a l ly N o n e s s e n t ia l - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
A r g in in e a A la n i n e H is t id i n e A s p a r a g i n e I s o le u c in e A s p a r ta te L e u c in e C y s te i n e L y s i n e G lu ta m a te M e th io n in e G lu ta m i n e P h e n y la la n i n e G l y c i n e T h r e o n in e P r o l in e T r y p to p h a n S e r in e V a l in e T y r o s in e
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - a “ N u tr i t io n a l l y s e m ie s s e n t ia l .” S y n t h e s iz e d a t r a te s in a d e q u a te to s u p p o r t g r o w t h o f c h i ld r e n .
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.
M. Zaharna Clini. Chem. 2009
Peptide bond
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.
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)
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)
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 chain of HbA, HbS is formed, which results in sickle-cell anemia.
M. Zaharna Clini. Chem. 2009
Secondary structure Initial helical
folding Beta pleated sheet Held together by
Hydrogen bonding
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
M. Zaharna Clini. Chem. 2009
Quaternary structure 2 or more polypeptide
chains binding together eg. Hemoglobin
Hemoglobin has 4 subunits
Two chains Two chains
Many enzymes have quaternary structures
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)
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
M. Zaharna Clini. Chem. 2009
Conjugated Proteins
Classification Prosthetic group
Example
Lipoprotein Lipid HDL
Glycoprotein Carbohydrates Immunoglo-bulins
Phosphoprotein Phosphate Casein of milk
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
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
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
HC
R
O
NH
CH
CO
RNH
CH
C
R
O
O–
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
HClPepsin
Protein Digestion – Small Intestine
Pancreatic enzymes secreted Trypsinogen Chymotrypsinogen Procarboxypeptidase Proelastase Collagenase
Zymogens
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
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
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
Protein Digestion Proteins are broken down to
Tripeptides Dipeptides Free amino acids
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+
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
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)
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
Groff & Gropper, 2000
Overview of Protein Digestion and Absorption in Monogastrics
OVERVIEW OF AMINO ACID METABOLISM
ENVIRONMENT ORGANISM
Ingested protein
Bio- synthesis Protein
AMINO ACIDS
Nitrogen Carbon
skeletons
Urea
Degradation (required)
1 2 3
a
b
PurinesPyrimidinesPorphyrins
c c
Used for energy
pyruvateα-ketoglutaratesuccinyl-CoAfumarateoxaloacetate
acetoacetateacetyl CoA
(glucogenic)
(ketogenic)
Amino Acid Catabolism Deamination of Amino Acids removal of the a-amino acids
Oxidative DeaminationNon-oxidative DeaminationTransamination
TRANSAMINATION
The term amphibolic is used to describe a biochemical pathway that involves both catabolism and anabolism
Reductive amination catalyzed byglutamate dehydrogenase (this is physiological
important becouse high conc. Of NH4 ion are cytotoxic)
Glutamine synthesis is coupled to hydrolysis of ATP
Pyruvate is an amphibolic intermediatein synthesis of alanine
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
Asparagine synthesis is energetically
favorable due to coupling to ATP hydrolysis
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)
Multistep pathway for glycine biosynthesis
Glycine is also synthesized from serine
Cysteine is not nutritionally essential, however it is derived from methionine
+NH3
CH
C
H2C
O-
O
H2C S CH3
Tyrosine is formedfrom phenylalanine
Hydroxyproline is formed after protein synthesis
Selenocysteine is synthesized from serine and selenophosphate
Amino acids that are synthesized de novo in humans. All are related by a small number of steps to glycolysis or TCA cycle intermediates.
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
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
UREA CYCLE
mitochondria
cytosol
Function: detoxification of ammonia (prevents hyperammonemia)
FATE OF THE CARBON SKELETONS
Carbon skeletons are used for energy.
Glucogenic: TCA cycle intermediates(gluconeogensis)
Ketogenic: acetyl CoA, acetoacetyl CoA, or acetoacetate
Protein synthesis On-going, semicontinuous activity
in all cells but rate varies greatly between tissues
Rate of protein synthesis
Ks (%/d)
Tissue Pig Steer
LiverGutMuscle
23455
21392
Ks = fraction of tissue protein synthesized per day
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
Protein degradation Also controlled by hormones and
energy status Method to assist in metabolic
control turns off enzymes
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
Changes in deposition
Synthesis Degradation Deposition
No change
No change
No change
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
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 )
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
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)
Urinary nitrogen excretion
Urine
KIDNEY
LIVER
Urea
Urea
CO2
Amino acids keto acids
NH3
Blood
Protein Synthesis
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
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
http://www.princeton.edu/%7Ehos/images/rna.gif
http://images2.clinicaltools.com/images/gene/dna_versus_rna_reversed.jpg
STEP 1: TRANSCRIPTION= making RNALocation: Eukaryotes-nucleusProkaryotes-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 The rest are the same C=G, T=A, G=C
Try this example. Using the following DNA sequence,
what would be the complementary RNA sequence?
ATCCGTAATTATGGC UAGGCAUUAAUACCG
http://www.odec.ca/projects/2004/mcgo4s0/public_html/t3/mRNA%20to%20protein.gif
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
Codon and Anticodon Codon-found on mRNA Anticodon-found on
tRNA
http://images.google.com/imgres?imgurl=http://www.obgynacademy.com/basicsciences/fetology/genetics/images/codon_GCA.gif&imgrefurl=http://www.obgynacademy.com/basicsciences/fetology/genetics/&usg=__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/Articleimages/kaiser/tRNA_arg.jpg
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
SUMMARY Transcription= process of making
RNA from DNA Translation= RNA directions are
used to make a protein from amino acids
• DNARNA Protein Transcription Translation
nucleus Cytoplasm on ribosome
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
Video Clips http://www.youtube.com/watch?v=
KvYEqGb7XN8&feature=related http://www.youtube.com/watch?v=
B6O6uRb1D38&feature=related
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.
Explain the steps in protein synthesis.
http://stemcells.nih.gov/info/scireport/images/figurea6.jpg
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
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
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
Protein Degradation in RumenFeedstuff % Degraded
in 2 hours
Urea 100
Alfalfa (fresh) 90
Wheat Grain 78
Soybean Meal 65
Corn Grain 48
Blood Meal 18
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)
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
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!)
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)
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
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)
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
Con
cent
ratio
n
Carbon backbone(from CHO fermentation)
Microbial Protein Formation
Dietary NPN
Dietary Soluble RDP
Microbial ProteinsAmino
Acids
Carbon Skeletons
Sulfur
Other Co-factors
NH3 ATP
Dietary Starch Sugar
Dietary Cellulose Hemicellulose
rapid
slow
rapid
slower
Dietary Insoluble RDP
very slow
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
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
Feed Protein, NPN and CHO
Feed Protein
Feed NPN
NH3/NH4
Bacterial N
NH4+ loss
MCP
RDP
RUPFeed Protein
AA
MCP
AA
NH3
Liver
Blood Urea
Salivary N
ATP
RUMEN
SMALL INTESTINE
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
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
Salivary Urea
NPN
NH3
POOL
Dietary Nitrogen Non-utili
zed Ammonia
NH3 UREA
LIVER
LEVEL TOPROVIDE FORMAXIMUMMICROBIAL GROWTH
MICROBIAL PROTEIN
65% OF PROTEIN
35% OF PROTEIN
SMALL INTESTINE
AMINO ACIDS
AMINO ACIDSPROTEIN
AMINO ACIDS
PEPTIDES
Reticulo-rumen
RUP
RDP
Recycled urea
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
Functional Proteins
Functional proteins are feed-derived proteins that, in addition to their nutritional value, produce a biological effect in the body
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
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
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
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
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
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
Protein Fragments That Have Biological Activity
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