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Natural plant enzyme inhibitors. Studies on a proteinase inhibitor from Italian millet ( Setaria italica )
Author(s) -
Udupa Saraswati,
Pattabiraman Thillaisthanam N.
Publication year - 1984
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740350615
Subject(s) - trypsin inhibitor , trypsin , sephadex , casein , chemistry , chromatography , biochemistry , chymotrypsin , kunitz sti protease inhibitor , thermolysin , enzyme
A proteinase inhibitor specific for trypsin was purified from Italian millet ( Setaria italica ) 170‐fold by extraction with 0.02 M HC1, ammonium sulphate fractionation, chromatography on CM‐cellulose and trypsin‐affigel chromatography. The inhibitor with an M r of 14000 was found to be homogeneous by gel chromatography on Sephadex G‐100 and sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. It reacted with bovine trypsin in a 1:1 stoichiometric fashion. Inhibition of trypsin was nearly double when assayed with benzoyl DL ‐arginine p ‐nitroanilide as substrate compared to the activity with casein as substrate. The inhibitor affected the tryptic activity in human and bovine pancreatic preparations to an equal extent. Chemical modification studies showed that amino groups, disulphide bridges and sulphydryl groups are essential for the action of the inhibitor. Pretreatment with porcine pepsin or bovine α‐chymotrypsin increased the antitryptic activity of the inhibitor when assayed with the low molecular weight substrate but not with casein.