Acid proteases proteinases

Peptidases are enzymes that catalyse the hydrolysis of peptide bonds - the bonds between amino acids that are found in peptides and proteins. The terms protease , proteinase and proteolytic enzyme are synonymous, but strictly speaking can only be applied to peptidases that hydrolase bonds in proteins. Because there are many peptidases that act only on peptides, the term peptidase is recommended. Peptidases are included in subclass 3.4 of enzyme nomenclature [1,5]. 

Proteases (proteinases, peptidases, or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. The process is called peptide cleavage, a common mechanism of activation or inactivation of enzymes. They use a molecule of water for this, and are thus classified as hydrolases. 

Enzymatic synthesis of aliphatic polyesters was also achieved by the ringopening polymerization of cyclic diesters. Lactide was not enzymatically polymerized under mild reaction conditions however, poly(lacfic acid) with the molecular weight higher than 1 x 10" was formed using lipase BC as catalyst at higher temperatures (80-130°C). Protease (proteinase K) also induced the polymerization however, the catalytic activity was relatively low. 

Lactide was polymerized by lipase PC in bulk at high temperature (80-130°C) to produce poly(lactic acid) with Mw up to 2.7 x 105 [64, 65]. The molecular weight of the polymer from the D,L-isomer was higher than that from the d,d- and L,L-ones. Protease (proteinase K) also induced the polymerization of lactide, however, the catalytic activity was relatively low. 

Aspartic Proteinases. This group of proteinases is named for the aspartic acid residue in the active site. Previously, this group of enzymes was often referred to as the "acid proteases" (4). Members of this group are generally found only in eukaryotic organisms. However, clear evidence has been presented that certain viruses, most importantly the virus (HIV-1) considered to give rise to autoimmune deficiency disease (AIDS), and the polio virus, contain coding sequences for a dimeric aspartic proteinase which is involved in the... 

Latent forms of a neutral protease and an acid protease (pH optimum 5.3) from cartilage are activated by trypsin hydrolysis to give Ca2+-dependent enzymes that catalyze the hydrolysis of proteoglycan.406 Some Ca2+-dependent proteinases are isolated as proenzymes that can be converted to the active form by high [Ca2+] or by low [Ca2+] in the presence of a digestable substrate.407... 

Storage proteins are hydrolysed into their constituent amino acids by proteinases (proteases), enzymes which have been classified into four major groups based on their active site catalytic mechanisms. These are ... 

The human organism is not able to use dietary proteins as such. They must be hydrolysed into single amino acid molecules before they can be absorbed. The hydrolysis of proteins (mostly denatured proteins) is catalysed by proteolytic enzymes called proteases (proteinases or peptidases), which have relatively high substrate specificity. They catalyse the hydrolysis of interior peptide bonds to form peptides of different sizes (endopeptidases such as pepsin, trypsin and chymotrypsin) or attack the terminal amino acids (exopeptidases). Hydrolysis of the N-terminal amino acids is... 

Proteases, which can be classified as either peptidases or proteinases. These cleave polypeptide chains eventually into their component amino acids. Peptidases can be further classified as endopeptidases (which act on the main-chain amido groups along the polypeptide molecule) or as exopeptidases (which act only at terminal amino acid residues). 

The NC-IUBMB has introduced a number of changes in the terminology following the proposals made by Barrett, Rawlings and co-workers [7] [8]. The term peptidase should now be used as a synonym for peptide hydrolase and includes all enzymes that hydrolyze peptide bonds. Previously the term peptidases was restricted to exopeptidases . The terms peptidase and protease are now synonymous. For consistency with this nomenclature, the term proteinases has been replaced by endopeptidases . To complete this note on terminology, we remind the reader that the terms cysteine endopeptidases and aspartic endopeptidases were previously called thiol proteinases and acid or carboxyl proteinases , respectively [9],... 

Peptide hydrolases (peptidases or proteases, i.e., enzymes hydrolyzing peptide bonds in peptides and proteins, see Chapt. 2) have received particular attention among hydrolases. As already described in Chapt. 2, peptidases are divided into exopeptidases (EC 3.4.11 -19), which cleave one or a few amino acids from the N- or C-terminus, and endopeptidas-es (proteinases, EC 3.4.21-99), which act internally in polypeptide chains [2], The presentation of enzymatic mechanisms of hydrolysis in the following sections will begin with peptidases and continue with other hydrolases such as esterases. 

The gross proteolysis of casein is probably due solely to rennet and plasmin activity (O Keeffe et al. 1978). Bacterial proteases and peptides are responsible for subsequent breakdown of the large peptides produced by rennet and plasmin into successively smaller peptides and finally amino acids (O Keeffe et al. 1978). If the relative rate of proteinase activity by rennet, plasmin, and bacterial proteases exceeds that of the bacterial peptidase system, bitterness in the cheese could result. Bitter peptides can be produced from a,-,- or /3-casein by the action of rennet or the activity of bacterial proteinase on /3-casein (Visser et al. 1983). The proteolytic breakdown of /3-casein and the subsequent development of bitterness are strongly retarded by the presence of salt (Fox and Walley 1971 Stadhouders et al. 1983). The principal source of bitter peptides in Gouda cheese is 3-casein, and more particularly the C-terminal region, i.e., 3(193-209) and 3(193-207) (Visser et al. 1983). In model systems, bitter peptides are completely debittered by a peptidases system of S. cremoris (Visser et al. 1983). 

Penicillium caseicolum produces an extracellular aspartyl proteinase and a metalloproteinase with properties very similar to those of the extracellular enzymes produced by P roqueforti (Trieu-Cout and Gripon 1981 Trieu-Cout et al. 1982). Breakdown of casein in mold-ripened cheese results from the synergistic action of rennet and the proteases of lactic streptococci and penicillia (Desmazeaud and Gripon 1977). Peptidases of both lactic acid bacteria and penicillia contribute to formation of free amino acid and nonprotein nitrogen (Gripon et al. 1977). 

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