Metal compound-mediated hydrolytic cleavage of oxidized insulin B chain:Regioselectivity and influence of peptide secondary structure

The interaction of oxidized insulin B chain (B) with cis‐Pd(en)Cl₂] (en=ethylenediamine), cis‐Pd‐(dtco‐3‐OH)Cl₂] (dtco‐3‐OH= dithiacyclooctan‐3‐ol) and CuCl₂ was studied by electrospray mass spectrometry. It is discovered that the binding of Pd(II) complexes and the sites of cleavage are highly dependent on the secondary structure and local environment of B. The hydrolytic cleavage of denatured B by Pd(II) complexes was monitored by HPLC. The reaction is regioselective and follows first order kinetics with half‐life of 4.8 days at 40^oC. Two amide bonds, i. e. at Leu6‐Cys7 and at Gly8‐Ser9, which are dose to the two potential Pd(II) binding sites His5 and His10, are selectively cleaved. In the case of Cu(II) ion as promoter, only one cleavage site was observed which is located at Gly8‐Ser9 bond. These results provide improved understanding on the design of artificial metallopeptidase.