What enzymes are responsible for hydrolyzing the proteins in foods?

Proteases, also called peptidases, are the enzymes that hydrolyze the peptide bonds between amino acids, playing a crucial role in protein digestion, protein turnover, and other physiological processes. Different proteases have specific preferences for the type of peptide bonds they cleave, and they can be classified based on their catalytic mechanism or their specificity. Here are some key proteases involved in hydrolyzing the proteins in foods:

1. Pepsin:

- Secreted by the stomach, pepsin is active in the acidic environment of the stomach (pH 1-2).

- It belongs to the class of aspartic proteases.

- Pepsin primarily hydrolyzes peptide bonds involving aromatic amino acids or dicarboxylic amino acids (Asp and Glu).

- Pepsin breaks down proteins into smaller polypeptides, initiating protein digestion.

2. Trypsin and Chymotrypsin:

- Produced by the pancreas, trypsin and chymotrypsin are secreted into the small intestine as inactive proenzymes (trypsinogen and chymotrypsinogen).

- Enteropeptidase, an enzyme present in the small intestine, activates trypsinogen to trypsin.

- Trypsin is a serine protease and is responsible for cleaving peptide bonds involving basic amino acids (Lys and Arg).

- Chymotrypsin is also a serine protease and preferentially hydrolyzes peptide bonds involving aromatic amino acids (Phe, Trp, and Tyr).

3. Elastase:

- Another pancreatic protease, elastase, plays a role in protein digestion.

- It specifically hydrolyzes peptide bonds involving small, non-polar amino acids (Ala, Gly, Ser, and Thr).

- Elastase is particularly active against elastin, a protein found in connective tissues.

4. Carboxypeptidases:

- Carboxypeptidases, produced by the pancreas, are exopeptidases that cleave amino acids from the C-terminal end of the polypeptide chains.

- Carboxypeptidase A preferentially releases aromatic or hydrophobic amino acids, while carboxypeptidase B releases basic amino acids.

5. Peptidases from Microorganisms:

- Some microorganisms also produce proteases that contribute to food fermentation and protein hydrolysis.

- Fungal proteases (e.g., from Aspergillus and Rhizopus) and bacterial proteases (e.g., from Bacillus and Lactobacillus) are commonly used in the food industry for various applications, such as cheese ripening, meat tenderization, and production of soy sauce.

These are some of the key proteases involved in hydrolyzing the proteins in foods. They work together to break down complex proteins into smaller peptides and amino acids, facilitating digestion and absorption of essential nutrients.