title: Trypsin and chymotrypsin inhibitor from chick peas. Selective chemical modifications of the inhibitor and isolation of two isoinhibitors.
abstract: The trypsin and chymotrypsin inhibitor from chick peas (CI) is stable in HCl 0.001 M -- 0.01 M and in KOH 0.01 M -- 0.05 M even after 24 h. Increased KOH concentrations decrease considerably the inhibitory activity already after 1 h. Maleyation and succinylation of the inhibitor resulted in almost full loss of its trypsin-inhibitory activity but had no effect on the chymotrypsin-inhibitory activity. A series of modifications directed towards tyrosyl residues showed that iodination influenced only the chymotrypsin-inhibitory activity; however, nitration and arsanilation affected not only the chymotrypsin-inhibitory activity but also the trypsin-inhibitory activity. Treatment of the inhibitor with CNBr and chloramine T resulted only in a decrease in the chymotrypsin-inhibitory activity indicating that the only methionine is involved in the chymotrypsin-inhibitory activity. When CI-fragment A, previously treated with trypsin at pH 3.75, was further treated with carboxypeptidase B, a release of three lysyl residues per mole protein was found. CI was separated by equilibrium chromatography on SP-Sephadex column into two isoinhibitors, CII and CIII, respectively. Both inhibited trypsin and chymotrypsin with the same specific activity as CI. They differed from each other only in a glutamyl, aspartyl, glycyl and alanyl residue.
mesh_terms: D000596:Amino Acids; D055598:Chemical Phenomena; D002621:Chemistry; D002918:Chymotrypsin / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D007887:Fabaceae / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D010946:Plants, Medicinal; D014361:Trypsin Inhibitors / Q000032:analysis / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D014361:Trypsin Inhibitors; D002918:Chymotrypsin