D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate = 3-(imidazol-4-yl)-2-oxopropyl phosphate + H2O Binds 2 manganese ions per subunit. Competitive inhibition by 3-amino-1,2,4-triazole (e.g. ATZ). kcat is 1000 sec(-1) with imidazoleglycerol-phosphate as substrate (at pH 7.7 and 37 degrees Celsius). Amino-acid biosynthesis; L-histidine biosynthesis; L-histidine from 5-phospho-alpha-D-ribose 1-diphosphate: step 6/9. Belongs to the imidazoleglycerol-phosphate dehydratase family.