EXTENSIVE CROSSLINKING BETWEEN SUBUNITS OF OLIGOMERIC PROTEINS INDUCED BY FUROCOUMARINS PLUS UV-A IRRADIATION

Abstract— Exposure of oligomeric proteins to UV-A irradiation in the presence of various furocoumarins results in extensive crosslinking of the enzyme subunits. The mechanism by which these covalent bridges are formed does not involve the furocoumarin moiety as the crosslinking agent, but depends upon oxidative processes, mainly involving singlet oxygen and radical mediated processes not involving oxygen. The formation of crosslinks is not per se responsible for the inactivation of enzymes since in glutamate dehydrogenase the two reactions proceed at the same rate, in catalase it is not accompanied by enzyme inactivation and in alcohol dehydrogenase the inactivation rate is higher than polymerization.