Purification and characterization of a trypsin inhibitor from rice bran.

Abstract
A trypsin inhibitor was isolated and purified from the bran of rice, O. sativa, by extraction with 1% sodium chloride, heat treatment, ammonium sulfate precipitation, ion-exchange chromatography on a CM-Sephadex C-25 and gel filtration on a Sephadex G-75. The final preparation was homogeneous by electrophoretic analysis. Rice bran trypsin inhibitor (RBTI) had a MW of .apprx. 14,500 and an isoelectric point of 8.07. The amino acid composition was characterized by high contents of basic amino acids, aspartic acid, glutamic acid, proline and cystine. BRTI inhibited bovine trypsin at an inhibitor-enzyme molar ratio of 1:1.6. It displayed an ability to inhibit .alpha.-chymotrypsin, pepsin, papain and subtilisin BPN [blood plasma nitrogen].

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