The biosynthesis of histidine; D-erythro-imidazoleglycerol phosphate dehydrase.

Reaction 2 is catalyzed by the enzyme imidazoleacetol phosphate transaminase (1). Reaction 3 is catalyzed by the enzyme L-histidinol phosphate phosphatase (2). Reaction 4 is catalyzed by the enzyme L-histidinol dehydrogenase (3, 4). This report is concerned with the purification and description of the enzyme from N. crassa catalyzing Reaction 1, the dehydration of D-erythroimidazoleglycerol phosphate. This enzyme will be called imidazoleglycerol phosphate dehydrase (IGP dehydrase). A preliminary report on this enzyme has appeared (5). The substrate used in these studies, n-erythro-imidazoleglycerol phosphate, has been synthesized chemically from n-ribose 5-phosphate and formamidine.