ON THE PRESENCE AND ACTIVITIES OF PROTEOLYTIC-ENZYMES IN VITAL WHEAT GLUTEN

Two vital wheat gluten samples were submitted to an Osborne type fract ionation. The proteolytic activities of the resulting fractions were e valuated. Gluten contained endoproteolytic, exoproteolytic, carboxypep tidase, aminopeptidase and N alpha-benzoylarginine-p-nitroanilide hydr olase activities. After extraction with 0.5 M NaCl, and subsequently w ith 70% (v/v) ethanol, little activity remained in the extracted glute n. 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-pol yacrylamide gel electrophoresis. The sum of lysine, leucine, phenylala nine, tyrosine and arginine accounted for ca. 40-44% of the released a mino acids, while they only make up ca. 18% of vital gluten proteins. Good correlations were found between the proportions of the amino acid s released by the different Osborne fractions as a result of autodiges tion, indicating that the gluten hydrolysing enzymes found in the diff erent 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 phenylmet hylsulphonylfluoride (1.0 mM), a serine protease inhibitor. (C) 1997 A cademic Press Limited.