Synthesis and characterization of covalent flavin–papain complexes with sulphur in the sulphide and sulphone oxidation states

Abstract

Two 2′,3′,4′,5′-tetra-acetylriboflavin derivatives of papain, differing in the oxidation state of the sulphur atom of Cys-25 which anchors the coenzyme species to the enzyme, have been synthesized by modification of the active site of papain with 8α-bromo-2′,3′,4′,5′-tetra-acetylriboflavin under different conditions.