NADPH-dependent melanin pigment formation from 5-hydroxyindolealkylamines by hepatic and cerebral microsomes

Abstract

Incubation of 5-hydroxytryptophan, 5-hydroxytryptamine, 5-hydroxytryptophol and 5-hydroxyindoleacetic acid with rat liver or brain microsomes in the presence of an NADPH-generating system and molecular oxygen caused the formation of microsomal protein-bound melanin-like pigment. The free radical property of this pigment was proved by electron spin resonance spectroscopy. The formation of the pigment was inhibited by superoxide dismutase which indicates the participation of superoxide anion radical in this type of melanogenesis.