University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

382

Pages:

5
Author:

Sheha A.

Types of proteases Exopeptidases: Carboxypeptidases and aminopeptidase hydrolyze only the terminal peptide bonds connected to the last amino acid residue of the peptide chain and release that terminal amino acid. Endopeptidases: pepsin, trypsin, chymotrypsin etc. hydrolyze specific peptide bonds deep in the middle of peptide chain to cleave the polypeptide chain into more than one smaller peptides. Digestion of protein begins in the stomach and continuous in the intestine. Digestion in Stomach Protein digestion starts in the stomach by: HCl Pepsin Rennin of the gastric juice. a) HCl: HCl secreted by the parietal cells of gastric gland HCl makes the pH optimum for the action of pepsin It activates pepsin HCl also hydrolyzes proteins but this will denature the proteins at high temperature So HCl cannot break peptide bonds at room temperature b) Rennin: Rennin is a protease It is active in infants and is involved in the curdling of milk. Rennin: Rennin curdles casein of milk to paracasein which then can easily be digested in adults. Pepsin: Pepsin is secreted by the chief cell of stomach as pepsinogen which is activated to pepsin by the action of HCl. Later pepsin itself converts pepsinogen to pepsin (autocatalysis). Pepsin is an endopeptidase hydrolyzing specific peptide bonds. Proteins are broken into polypeptides of lower molecular weight proteins and peptones by pepsin.