BIOGENESIS AND METABOLISM OF 5-HYDROXYINDOLE COMPOUNDS

Abstract

Until recently the only 5-hydroxyindole compounds known to occur in nature were bufotenine (N, N-dimethyl-5-hydroxytryptamine) and its derivatives which had been isolated from toad venom (1, 2). The isolation and identification of “serotonin” as 5-hydroxytryptamine (511TA) by Rapport et al. (3, 4) and its identification with the “enteramine” of Erspamer and Ottolenghi (5) a.nd the “thrombocytin” of Rand and Reid (6) renewed interest in 5-hydroxyindole compounds. Since then a large number of additional 5-hydroxyindole compounds have been found in nature. Both 5-hydroxytryptophan (7) and violacein, a pigment containing 5-hydroxyindole (S), have been found in Chromobacterium violaceum. 5HTA and its N-methylated analogues occur in almost all invertebrate and vertebrate species investigated (9). N , N-Dimethyl-5-hydroxytryptamine has also been isolated from plant sources such as the seeds of Piptadenia peregrina (10) and the toxic mushroom Amanita phalloides (11). 5-Hydroxyindoleacetic acid (5HIAA) has been found in mammalian urine (9, 12) and in the seeds of P. peregrina.’ The scheme shown in Fig. 1 connects these scattered observations into a pathway of metabolism starting with tryptophan and proceeding through 5-hydroxytryptophan to the various 5-hydroxyindole compounds. Evidence is presented for occurrence of many steps of this pathway in a number of organisms and tissues.