BIOCHEMISTRY

1. DIGESTION AND ABSORPTION OF
PROTEINS
V.S.RAVIKIRAN, MSc.

2. V.S.RAVIKIRAN, MSc.,
Department of Biochemistry,
ASRAM Medical college,
Eluru-534005.AP, India.
vsravikiran2013@gmail.com

8. Action of proteolytic enzymes
Enzyme Hydrolysis of bonds formed by
carboxyl groups of
Pepsin Phe, Tyr, Trp, Met
Trypsin Arg, Lys
Chymotrypsin Phe, Tyr, Trp, Val, Leu
Elastase Ala, Gly, Ser
Carboxypeptidase A C-terminal aromatic amino acids
Caroboxypeptidase B C-terminal basic amino acids

9. PROTEASES (Peptide hydrolases)
Exopeptidases or peptidases Endopeptidases or proteinases
 Aminopeptidases
 Dipeptidyl peptidases  Serine proteinases (active center has
serine group), e.g. Trypsin
 Tripeptidyl peptidases Cysteine proteinases (active center
has Cysteine group), e.g. Papain
 Carboxypeptidases Aspartic proteinases (active center
has Aspartic group), e.g. Pepsin
 Peptidyl dipeptidases
 Dipeptidases
 Tripeptidases  Metalloproteinase proteinases
(active center has metal group)
 Omega peptidases

19. (A,V,L I,M.F Y)
(K,R, C)
(D,E)
(P,G)

20. INTESTINE, BRAIN, KIDNEY TUBULES
NEUTRAL AMINO ACID

24. Clinical applications:
Abnormalities in protein and amino acids digestion
and absorption:
↓5-oxoprolinase Oxoprolinuria (pyroglutamic
aciduria)
 Partial gastrectomy, pancreatitis, carcinoma of pancreas and cystic
fibrosis (CF)
Protein losing enteropathy

26. Defects in intestinal amino acid
transport system:
Hartnup’s disease
Imino glycinuria
Cystinuria
Lysinuric protein intoletence
Oasthouse syndrome

28. Cystinuria:

29. Intracellular protein degradation:

30. Cathepsins:
 is a Greek word, meaning ‘to digest’
 present in phagolysosomes
 are 18 in numbers; designated as A-T
 most of them are active around pH 5
 Cathepsin N – collagenolytic cathepsin
 Cathepsin R: degradation of ribosomes
 Cathepsin B: seen extracellularly in pathological conditions

31. Ubiquitin pathway:
 a 76-residue monomeric protein
 seen in all cells abundantly
 is tag for protein degradation and needs ATP and three enzymes
 Ubiquitin attached proteins are immediately broken down in
proteasomes.

32. Proteosomes:
 proteasome assembly has a molecular weight of 2000 kD with 28
subunits and has a central cylindrical hollow core.
 Ubiquitin tagged proteins are taken into this barrel, and surrounding
proteolytic enzymes digest the protein into small oligopeptides (5-6
aa).
 Proteosome degradation is also ATP dependent.

33. Inter-organ Transport of Amino Acids
• Post absorptive (fasting) • After food
Alanine
Glutamine
Valine
Alanine
Glutamine
Alanine
Valine
Brain
Kidney
Muscle
Liver
Gut

34. THE END
THANKS FORYOUR
ATTENTION