The Journal of Biochemistry
Online ISSN : 1756-2651
Print ISSN : 0021-924X
Studies on Soybean Trypsin Inhibitors
XI. Complete Amino Acid Sequence of a Soybean Trypsin-Chymotrypsin-Elastase Inhibitor, C-II
Shoji ODANITokuji IKENAKA
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JOURNAL FREE ACCESS

1977 Volume 82 Issue 6 Pages 1523-1531

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Abstract

Soybean inhibitor C-II, which inhibits trypsin, α-chymotrypsin, and elastase, was reduced and S-carboxymethylated, and digested with trypsin. The amino acid sequences of the resulting tryptic peptides were determined by conventional methods, establishing the complete 76-amino acid sequence of the inhibitor.
Inhibitor C-II was found to be homologous with soybean (Glycine max) Bowman-Birk inhibitor and more closely related to an inhibitor from garden beans (Phaseolus vulgaris). The homology with these inhibitors and the limited proteolysis of C-II indicated the reactive sites of C-II for elastase and trypsin to be alanine-22 and arginine-49, respectively. Arginine-49 was also identified as a reactive site for α-chymotrypsin. It was found that only a few replacements of one or two amino acid residues around the reactive sites resulted in considerable alteration of the inhibitory specificity.

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© The Japanese Biochemical Society
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