amino-acid biosynthesis nonprotein amino-acid biosynthesis histidine metabolism organosulfur biosynthesis ergothioneine biosynthesis UPa:UPA01014 PMID:20420449 Biosynthesis of ergothioneine. Ergothioneine is a histidine-derived thiol of bacterial and fungal origin that has also been isolated from animal and human tissue. Ergothioneine has antioxidant properties. MetaCyc:PWY-7255 GO:0052699 pathway