Proline-specific peptidases

In addition to phosphotriesterase from P. diminuta (PTE) discussed above, two other types of enzymes were found to exhibit phosphotriesterase activity. Interestingly, both are peptidases - the enzymes which in nature hydrolyse a peptide bond. The first one - organophosphorus acid anhydrolase (OPAA) from Alteromonas sp. JD6.5 - is a proline dipeptidase its original activity is to cleave a dipepfide bond with a prolyl residue at the carboxy terminus. The second one - aminopeptidase P (AMPP) from Escherichia coli - is a proline-specific peptidase that catalyses hydrolysis of N-terminal peptide bonds containing a proline residue. ° ... 

The starter cells begin to die off at the end of curd manufacture (Figure 10.21) the dead cells may lyse and release their intracellular endopeptidases (Pep O, Pep F), aminopeptidases (including Pep N, Pep A, Pep C, Pep X), tripeptidases and dipeptidases (including proline-specific peptidases) which produce a range of free amino acids (Figure 10.22). About 150 peptides have... 

Figure 10-2 Mode of Action of Proline-Specific Peptidases. Source Reprinted with permission from M.B. Habibi-Najafi and B.H. Lee, Bitterness in Cheese A Review, Crit. Rev. Food Sci. Nutr., Vol. 36, No. 5, p. 408. Copyright CRC Press, Boca Raton, Florida.

Proline-specific peptidases can hydrolyze proUne residues from the A-terminal position of peptides. Proline iminopeptidase (PepI) has aminopeptidase activity towards A-terminal proline peptides and prefers tri-peptides (NH2-Pro, Xn-COOH). The prolinase PepR has a broad specificity for dipeptides (NH2-ProiX-COOH). These proline-specific peptidases are absent from all L. lactis strains. The activity of cell extract fi-om Lact. helveticus and Lact. rhamnosus for several proline dipeptides was significantly reduced in PepR-deletion mutant. Those observations suggest that PepI and PepR may contribute to the specific proteolytic capacity for breaking down peptides containing proline in Lactobacillus strains (Liu et al. 2010). 

Augustyns, K., der Veken, P.V., Senten, K. and Haemers, A. (2005) The therapeutic potential of inhibitors of dipeptidyl peptidase IV (DPP-IV) and related proline-specific dipeptidyl aminopeptidases. Current Medicinal Chemistry, 12, 971-998 (c) Augustyns, K., der Veken, P.V. and Haemers, A. 

Inhibitors of proline-specific dipeptidyl peptidases DPP-4 inhibitors as a novel approach for the treatment of type 2 diabetes. Expert Opinion on Therapeutic Patents, 15, 1387-1407 (d) von Geldern, T.W. and Trevillyan, J.M. 

Specific peptidase and protease systems which involve Mn(II) include thrombin limited-proteolysis of prothrombin [122], insulin protease [123], enkephalin-degrading amino-peptidase [124], camosinase [125,129], ki-ninase [127], and trypsin activation [128]. A metalIo(Mn)-protease is involved in the processing of mitochondrial precursor proteins [130]. Several aminopeptidases are also specifically manganese-dependent, namely Leu-aminopeptidase [131] and prolidase or C-terminal proline dipeptidase [132-135]. Other systems that hydrolyze linear and cyclic G-N bonds include various amino-acylases, deacetylases, amidases and methylene-... 

Dipeptidyl peptidase 4 (DPP-4) is a ubiquitous proline-specific serine protease responsible for the rapid inactivation of inaetins, including glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide. To alleviate the inactivation of GLP-1, inhibitors of DPP-IV are being evaluated for their abihty to provide improved control of blood glucose for diabetics [187-189]. 

Carboxypeptidase A catalyzes the hydrolysis of carboxyl-terminal acidic or neutral amino acids however, the rate of hydrolysis depends on the structure of the side chain R. Amino acids with nonpolar aryl or alkyl side chains are cleaved more rapidly. Carboxypeptidase B is specific for the hydrolysis of basic COOH-terminal amino acids (lysine and arginine). Neither peptidase functions if proline occupies the COOH-terminal position or is the next to last amino acid. 

Although any of several combinations of proteases can be used, ideally, one or more non-specific endopeptidases should be used first to convert the protein into many small peptides. These small peptides can then be degraded to amino acids by aminopeptidases and prolidase (hydrolyzes X-Pro bonds). Sometimes, carboxypeptidases are also used. Although leucine aminopeptidase has been used as the amino-peptidase (see Hill and Schmidt 1962), it may be preferable to use aminopeptidase M (Rohm and Haas, supplied by Henley and Co. of N.Y.), since this enzyme removes most residues at acceptable rates. Leucine aminopeptidase removes hydrophobic residues most rapidly, whereas some other residues are removed very slowly. Most procedures should probably include the use of prolidase (Miles) since many aminopeptidases do not cleave X-Pro bonds at appreciable rates. If it is found that proline is not released quantitatively by these procedures, the use of citrus leaf carboxypeptidase C (Rohm and Haas) can be tried after the initial endopeptidase hydrolysis and before the addition of aminopeptidase M and prolidase. Carboxypeptidase C (also yeast carboxypeptidase Y - see Hayashi et al. 1973) hydrolyzes proline bonds (as well as all others), but if proline is at or adjacent to the NH2 terminus of a peptide, it would probably not be released. In all procedures a control consisting of the enzymes only should be run in parallel with the hydrolyzed sample, and corrections should be made for any amino acids found by analysis of the control. suhic / /< > , mi... 

Ritt, J.-F., Remize, F., Grandvalet, C., et al. (2009) Peptidases specific for proline-containing peptides and their unusual peptide-dependent regulation in Oenococcus oeni. J Appl Microbiol 106, 801-813. 

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