Cleavage of human orosomucoid by a chromium(V) species: relevance in biotoxicity of chromium

A chromium(V) complex, CrO(salen)+, was generated in situ and its interaction with human orosomucoid (alpha1-acid glycoprotein) has been evaluated. The chromium(V) species has been found to oxidize the protein rapidly. A second order rate constant of 5 +/- 0.4 x 10(4) M(-1) s(-1) has been obtained for the redox process. Gel electrophoresis pattern of AGP in the presence of metal ion clearly reveals the decrease in the intensity of the AGP band with the subsequent formation of protein fragments of lower molecular weight. At higher metal ion concentration a continuous smear is observed which indicates the nonselective cleavage of the glycoprotein. Cleavage of AGP is through the direct pathway of oxidation by a highly reactive chromium(V) species.