Endoproteinase

Related Reading

Introductions of Peptidase

Peptidases are enzymes that can hydrolyze peptide chains and can be divided into two main types, namely endopeptidases and exopeptidases, where endopeptidases act on specific peptide bonds within the polypeptide chain, such as pepsin, trypsin and chymotrypsin present in the animal digestive tract, and these enzymes are specific for peptide bonds composed of different amino acids. The enzymes that act on the peptide bonds at both ends of the protein peptide chain, those that act on the amino-terminal peptide bond are called aminopeptidases, and those that act on the carboxy-terminal peptide bond are called carboxypeptidases. Food protein is broken down into free amino acids in the digestive tract through the continuous action of various peptidases.

Endopeptidase

Endopeptidases, also commonly known as proteases, mainly act on the peptide bonds within protein polypeptide chains to break down long protein chains into short peptide fragments. Proteases are divided into different clans based on structural homology, and subclasses are further divided into different families based on the degree of sequence homology. When proteases hydrolyze proteins, the site of action varies depending on the type of peptide bond. For example, trypsin requires a peptide bond with basic amino acids (arginine, lysine) on the carboxyl side of the cut point; pepsin requires aromatic amino acids at both ends of the cut point; Bacillus subtilis basic protease requires hydrophobic aromatic amino acids (tryptophan, tyrosine, phenylalanine) on the carboxyl side of the cut point. The specificity of the cut site required by this protease is called substrate specificity of the protease. The substrate specificity of proteases can be used to obtain peptides with specific structures in a targeted manner.

Examples of Endopeptidases

Food Quality Impact

Cocoa

During fermentation of cocoa beans, a dominant endopeptidase (aspartate endopeptidase, optimum pH 3.5) and a carboxypeptidase (optimum pH 5.8) are secreted. Cocoa carboxypeptidase cannot hydrolyze Arg, Lys and Pro residues at the carboxyl terminus, and is more suitable for hydrophobic amino acids, and is slow to hydrolyze acidic amino acids. The hydrophobic free amino acids and hydrophilic peptides produced by the action of these two enzymes produce the characteristic aroma precursors of cocoa.

Cheese

In addition to microbial cells, cheese extracts also contain extracellular and extracellular peptidase activity. The exopeptidases released by microbial autolysis play a very important role in the degradation of casein oligopeptides. When soft cheeses are made with Penicillium camembert and Penicillium albicans, the ripening of the cheese is mainly controlled by protein hydrolytic enzymes. Capsule-treated recombinant aminopeptidase shortened the fermentation process of cheddar cheese and was able to improve the sensory evaluation scores of the cheese.