D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate = 3-(imidazol-4-yl)-2-oxopropyl phosphate + H2O Binds 2 manganese ions per subunit. 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. This protein is inactive in the dairy strain IL1403. The histidine biosynthesis pathway is not functional in the dairy strain IL1403.