title: Partial characterization of a subtilisin inhibitor from black bean seeds.
abstract: The subtilisin inhibitor (SI), isolated from black beans (Phaseolus vagaris) has a molecular weight of 8918 and it contains four half cystine residues. The N-terminal residue is arginine and the C-terminal is lysine. The subtilisin inhibiting site is composed of an Ala-Leu or Ile bond. This site interacts in addition to subtilisin (S) with elastase from human leukocytes (HLE), both of which compete for the inhibitor. Also, HLE-cleaved SI (SIHLE) is inactive against HLE as well as against S. It was shown that the inhibition of S by SI resembles a temporary inhibition, involving a very slow release of enzyme activity. The trypsin reactive site is a Lys-Val bond, and its interaction with bovine trypsin is very weak. No complexes of SI or trypsin-cleaved SI (SIT) with trypsin could be detected on cellulose-acetate membrane electrophoresis, while SIT forms a clearly visible complex with S.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D006801:Humans; D007700:Kinetics; D007962:Leukocytes / Q000201:enzymology; D010196:Pancreatic Elastase / Q000097:blood; D010446:Peptide Fragments / Q000032:analysis; D012639:Seeds / Q000032:analysis*; D013379:Substrate Specificity; D013381:Subtilisins / Q000037:antagonists & inhibitors*
chemical_list: D000596:Amino Acids; D010446:Peptide Fragments; D013381:Subtilisins; D010196:Pancreatic Elastase