title: Spontaneous, non-enzymatic breakdown of peptides during enzymatic protein hydrolysis.
abstract: It is expected that during the hydrolysis of proteins with specific enzymes only peptides are formed that result from hydrolysis of the specific cleavage sites (i.e. specific peptides). It is, however, quite common to find a-specific peptides (i.e. resulting from a-specific cleavage), which are often ignored, or explained by impurities in the enzyme preparation. In recent work in a whey protein isolate (WPI) hydrolysate obtained with the specific Bacillus licheniformis protease (BLP), 13 peptides of 77 identified were found to be the result of a-specific cleavage. These were formed after degradation of 6 specific peptides, after 5 different types of amino acids. The fact that other peptides were not hydrolyzed after these 5 amino acids suggests that the cleavages were not the result of a contamination with a different enzyme. In other systems, certain peptide sequences have been described to degrade chemically, under relatively mild conditions. This process is referred to as spontaneous cleavage. To test if the a-specific peptides observed in the WPI hydrolysis are the results of spontaneous cleavages, the parental peptides were synthesized. Surprisingly, 4 of the 5 synthesized peptides were indeed spontaneously cleaved under the mild conditions used in this study (i.e. 40°C and pH 8) showing that peptides are less stable than typically considered. The rate of cleavage on the a-specific bonds was found to be enhanced in the presence of BLP. This suggests that the formation of a-specific peptides is not due to side activity but rather an enhancement of intrinsic instability of the peptides.
authors: Laboratory of Food Chemistry, Wageningen University, P.O. 17, 6700 AA Wageningen, The Netherlands. Electronic address: claire.butre@wur.nl.
authors: Claire I
authors: CI
authors: Butré
authors: Department of Food Science, University of Parma, Parco Area delle Scienze 59/A, 43124 Parma, Italy. Electronic address: sofie.buhler@yahoo.it.
authors: Sofie
authors: S
authors: Buhler
authors: Laboratory of Food Chemistry, Wageningen University, P.O. 17, 6700 AA Wageningen, The Netherlands; Department of Food Science, University of Parma, Parco Area delle Scienze 59/A, 43124 Parma, Italy. Electronic address: stefano.sforza@unipr.it.
authors: Stefano
authors: S
authors: Sforza
authors: Laboratory of Food Chemistry, Wageningen University, P.O. 17, 6700 AA Wageningen, The Netherlands. Electronic address: harry.gruppen@wur.nl.
authors: Harry
authors: H
authors: Gruppen
authors: Laboratory of Food Chemistry, Wageningen University, P.O. 17, 6700 AA Wageningen, The Netherlands. Electronic address: peter.wierenga@wur.nl.
authors: Peter A
authors: PA
authors: Wierenga
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry*; D010447:Peptide Hydrolases / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D059748:Proteolysis
chemical_list: D001426:Bacterial Proteins; D008894:Milk Proteins; D010455:Peptides; D010447:Peptide Hydrolases
keywords: A-specific cleavage; Cleavage site; LC–MS; Protease; Proteolysis; Synthetic peptide