title: Inhibition mechanism of a peanut trypsin-chymotrypsin inhibitor, B-III: determination of the reactive sites for trypsin and chymotrypsin.
abstract: Peanut inhibitor B-III was found to form two types of complexes with trypsin, T2I and TI, by gel filtration HPLC. Two cleaved peptide bonds, Arg(10)-Arg(11) and Arg(38)-Ser(39), in the trypsin modified inhibitor (TM-B-III*R*S) (J. Biochem. 93, 479-485 (1983] were resynthesized by the complex formation with 2 mol of trypsin. These results suggest that the two peptide bonds may be the reactive sites for trypsin. TM-B-III*R*S inhibited bovine trypsin as well as native B-III but had little chymotrypsin inhibitory activity. The two peptide bonds, Arg(10)-Arg(11) and Arg(38)-Ser(39), in B-III were cleaved partly by prolonged incubation with a catalytic amount of chymotrypsin. But gel filtration HPLC of the chymotrypsin-inhibitor complex showed the formation of only CI complex. Incubation of TM-B-III*R*S with an equimolar amount of chymotrypsin resulted in the resynthesis of only the Arg(10)-Arg(11) bond. These findings suggest that Arg(10)-Arg(11) may be a true reactive site for chymotrypsin. An inhibition mechanism of B-III against trypsin and chymotrypsin was proposed from the results obtained by the present studies.
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D010446:Peptide Fragments / Q000032:analysis; D010940:Plant Proteins; D011485:Protein Binding; D011487:Protein Conformation; D014357:Trypsin / Q000378:metabolism*; D014361:Trypsin Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D010446:Peptide Fragments; D010940:Plant Proteins; D014361:Trypsin Inhibitors; C037954:trypsin-chymotrypsin inhibitor B-III, peanut; D002918:Chymotrypsin; D014357:Trypsin