The biosynthesis of ergothioneine and histidine by Claviceps purpurea. 1. The incorporation of [2-14C]-acetate

Abstract

The growth of Claviceps purpurea in liquid shake culture, and methods for detection, estimation and isolation of ergothioneine from these cultures are described. Methods for degradation of ergothioneine on a micro scale are given. Isolation of histidine from a protein hydrolysate, and its degradation, are described. Degradation of ergothioneine and histidine isolated from a culture of C. purpurea grown on a medium containing (2-C14 ) acetate show that the pathways of biosynthesis of these 2 compounds are identical. The major contribution of acetate to the ergothioneine molecule is in the provision of one-carbon moieties, and the highest labelling was in the carbon-2 of the imidazole ring, followed by the methyl groups of the betaine. The residual 5-carbon chain was labelled to a lesser extent. Distribution of isotope in this chain precludes the possibility of it having been derived from glutamate formed via the citric acid cycle. Evidence was obtained that acetate was incorporated into other amino acids via the citric acid cycle. Continual subculturing has produced a strain of C. purpurea with pigmented conidia and in which the yield of ergothioneine is steadily increasing. Ergothioneine production by C. purpurea is independent of both alkaloid and sclerotia formation. The ergothioneine was found wholly or principally in the conidia.