Ordinary Digestive Enzymes

Procedures to obtain reliable enzyme kinetic parameters are discussed. The classification of enzymes regarding their function (substrate specificity and mechanism, Enzyme Commission Nomenclature) and protein families (MEROPS, CAZy, and Brenda platforms) is presented. The mechanism of the enzymes acting on the major nutrient substrates is described. The substrates discussed are carbohydrates (starch, oligosaccharides, and disaccharides); peptides (proteins, oligopeptides, and dipeptides); and acylglycerol esters (triacylglycerols and phospholipids). The enzymes discussed in detail are: serine endopeptidases (trypsins, chymotrypsins, elastases); collagenases; carboxypeptidases; aminopeptidases; amylases; α-glucosidases; β-glucosidases; β-fructosidases; β-N-acetylhexosaminidases; α-mannosidases; α-galactosidases; myrosinases; trehalases; triacylglycerol lipases; and phospholipases. Lysosomal proteins recruited as digestive enzymes (cysteine- and aspartic-endopeptidases) and enzymes involved in the degradation of cell walls are the subject of specific chapters.