Phenolases and melanogenesis in the coelomic fluid of the echinoid Diadema antillarum Phillippi

Abstract

Melanin is formed with in the coelomic amoebocytes of Diadema when exposed to air in vitro by a process of oxidation involving enzymes. It appears in association with spheroidal inclusions. An enzyme system with both mono- and polyphenolase activity has been demonstrated in the amoebocytes, which is affected by the same factors, and in the same way, as the production of pigment. Although the enzyme system and its substrate co-exist in the amoebocytes, pigment is not formed in them whilst they are in the perivisceral coelom. A heat-labile factor inhibiting the action of the phenolase system and the formation of melanin is present in the coelomic fluid but not in the amoebocytes. There is some evidence indicating that the enzyme system is localized in or around the spheroids, an area of relatively high oxidation-reduction potential, in which black pigment appears, especially after exposure to ultra-violet light. In the light, of these facts, a concept of melanogenesis in the sea urchin is advanced.