THE BIOSYNTHESIS OF NIKKOMYCIN-X FROM HISTIDINE IN STREPTOMYCES-TENDAE

L-Histidine (4) is the source in Streptomyces tendae for the imidazolo ne moiety (1) of nikkomycin X (2). It is deduced to be incorporated wi th stereospecific retention of the beta-pro-S proton. Histamine (5), 4 -formylimidazole (7) and 4-hydroxymethylimidazole (8) are not signific ant precursors. Urocanic acid (6) is a less efficient precursor than ( 4). Aldolase activity is identified in S.tendae which catalyses cleava ge of threo-(4-hydroxyphenyl)serine (9) but not significantly of threo - or erythro-beta-hydroxyhistidine.