1-(5-phospho-beta-D-ribosyl)-5'-AMP + H2O = 1-(5-phospho-beta-D-ribosyl)-5-[(5-phospho-beta-D-ribosylamino)methylideneamino]imidazole-4-carboxamide 1-(5-phospho-beta-D-ribosyl)-ATP + H2O = 1-(5-phospho-beta-D-ribosyl)-5'-AMP + diphosphate + H(+) Amino-acid biosynthesis; L-histidine biosynthesis; L-histidine from 5-phospho-alpha-D-ribose 1-diphosphate: step 2/9. Amino-acid biosynthesis; L-histidine biosynthesis; L-histidine from 5-phospho-alpha-D-ribose 1-diphosphate: step 3/9. In contrast to other fungi which have a single histidine biosynthesis trifunctional protein, 2 proteins are present in S.pombe to ensure these functions: his7 (phosphoribosyl-AMP cyclohydrolase and phosphoribosyl-ATP pyrophosphatase activities) and his2 (histidinol dehydrogenase activity).