Journal of Cereal Science vol:26 issue:2 pages:183-193
Two vital wheat gluten samples were submitted to an Osborne type fractionation. The proteolytic activities of the resulting fractions were evaluated. Gluten contained endoproteolytic, exoproteolytic, carboxypeptidase, aminopeptidase and N alpha-benzoylarginine-p-nitroanilide hydrolase activities. After extraction with 0.5 M NaCl, and subsequently with 70% (v/v) ethanol, little activity remained in the extracted gluten. Upon autodigestion of gluten no (microbial) enzymes were released. High specificities of gluten-associated proteolytic enzymes were noted and their effects were clearly visible on sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The sum of lysine, leucine, phenylalanine, tyrosine and arginine accounted for ca. 40-44% of the released amino acids, while they only make up ca. 18% of vital gluten proteins. Good correlations were found between the proportions of the amino acids released by the different Osborne fractions as a result of autodigestion, indicating that the gluten hydrolysing enzymes found in the different Osborne fractions are probably the same. Autodigestion of gluten proteins was reduced by ca. 73-76% upon addition of pepstatin A (0.2 mM), an inhibitor of aspartic proteases, and by c. 39-41% by phenylmethylsulphonylfluoride (1.0 mM), a serine protease inhibitor. (C) 1997 Academic Press Limited.