Fig. 1

Metabolism of AICAR to ATP is an essential step in His synthesis. Prs ribose-phosphate diphosphokinase, ATP adenosine triphosphate, R5F ribose 5-phosphate, PRPP phosphoribosyl pyrophosphate, PR-ATP phosphoribosyl-ATP, PR-AMP phosphoribosyl-AMP, PR-F-AICAR-P phosphoribosylformimino-AICAR-phosphate, PR-FAR phosphoribulosylformimino-AICAR-phosphate, AICAR 5-aminoimidazole-4-carboxamide ribonucleotide, FAICAR 5′-phosphoribosyl-5-formamido-4-imidazole carboxamide, IMP inosine 5′-phosphate, AS adenylosuccinate, AMP adenosine monophosphate, ADP adenosine diphosphate, IGP imidazole glycerol phosphate, IA-P imidazole acetol-phosphate, His-ol-P l-histidinol-phosphate, His-ol histidinol, Histidine l-histidine, HisG ATP-phosphoribosyltransferase, HisIE bifunctional enzyme (HisE phosphoribosyl-ATP pyrophosphatase, HisI phosphoribosyl-AMP cyclohydrolase), HisA phosphoribosylformimino-5-amino-1-phosphoribosyl-4-imidazole carboxamide isomerase, HisHF IGP synthase, HisB bifunctional imidazoleglycerol-phosphate dehydratase/histidinol-phosphatase, HisC histidinol-phosphate aminotransferase, HisD bifunctional histidinal dehydrogenase/histidinol dehydrogenase, PurH bifunctional AICAR transformylase/IMP cyclohydrolase, PurA adenylosuccinate synthetase, PurB adenylosuccinate lyase, Adk adenylate kinase, Gln glutamine, Glu glutamate, fTHF formyltetrahydrofolate, THF tetrahydrofolate, Asp aspartate, GTP guanosine-triphosphate, GDP guanosine-diphosphate, PP _i inorganic pyrophosphate, P _i inorganic phosphate, NAD⁺/NADH nicotinamide adenine dinucleotide oxidized/reduced form, fum fumaric acid. Feedback inhibition by His is indicated by red line; competitive inhibitions by ATP-PRT, AMP and ADP are indicated by dot lines; suggested competitive inhibition by AICAR is indicated by the red dot line