COBALT(III)-LIGATED PEPTIDES AS ACYL ACCEPTORS IN PEPTIDE-SYNTHESIS CATALYZED BY CHYMOTRYPSIN

The efficiency of cobalt(III)-ligated peptides as acceptor nucleophile s in acyl transfer reactions catalyzed by alpha-chymotrypsin was exami ned. A series of metallopeptides with the general formula [H-(Gly)(n)- OCo(NH3)(5)](2+) (1 less than or equal to n less than or equal to 4) w as tested. The aminolysis rate of acyl-chymotrypsin was measured spect rophotometrically by monitoring the concentration of unreacted nucleop hile. The rate of the competing hydrolysis of acyl-chymotrypsin was ob tained by automatic titration with base, using a pH-stat. The main res ult was that the positively charged metallopeptides, in general, were more efficient nucleophiles than the corresponding amides and free pep tides that were examined for comparison. A binding model that rational izes the findings is given.