The Biosynthesis of Histidine

It was later shown (2) that the mutant C84 accumulates imidazoleglycerol’ in the growth medium, that mutant Cl41 accumulates imidazoleglycerol and imidazoleacetol,2 and that T1710 accumulates L-histidinol.3 It was also observed that none of these compounds will replace histidine in promoting the growth of these mutants or other mutants blocked earlier in the sequence. This suggested that these imidazole compounds might be derived from biosynthetic intermediates such as phosphate esters to which Neurospora mycelium is impermeable. Preliminary evidence that certain of these mutants do accumulate phosphorylated imidazoleglycerol and imidazoleacetol has been presented (2). This is a report on the isolation and characterization of D-erythro-imidazoleglycerol phosphate (IGP), imidazoleacetol phosphate (IAP), and L-histidinol phosphate, which are accumulated in the mycelia of several of these mutants.