Secondary Products Synthesized from L-Histidine

L-Histidine, imidazolyl L-alanine, is one of the rare natural substances with an imidazole ring. In the secondary products derived from L-histidine the imidazole ring may be substituted and the alanyl side chain may be modified. In some compounds an additional heterocyclic ring is present, involving the C-atoms and the amino group of the side chain. 

Secondary L-histidine derivatives are formed in microorganisms, plants, and animals. 

Formation of L-histidine is closely related to purine biosynthesis (D 10.4, Fig. 239). ATP is the actual precursor. It condenses with phosphoribosyl pyrophosphate at position 1 before the purine ring is splitted between the positions 1 and 6. An Amadori rearrangement in the two-prime-ribose unit yields the ribulose derivative l-(5 -phosphoribosyl)-4-carboxamido-5-iV-(N -5 -phospho-ribosyl)-formamidinoimidazole, which reacts with glutamine to D-erythro-imidazole glycerol phosphate (the precursor of histidine) and l-(5 -phospho-ribosyl)-4-carboxamido-5-aminoimidazole, which may be regenerated to ATP (D 10.4). 

L-Histidine is the precursor of several types of secondary products  

1 ATP phosphoribosyltransferase 2 phosphoribosyl-ATP pyrophosphatase 3 phosphoribosyl-AMP cyclohydrolase 4 isomerase 5 formyltransferase, inosine monophosphate cyclohydrolase 6 adenylosuccinate synthetase 7 adenylosuccinate lyase 8 adenylate kinase 9 imidazole glycerol phosphate dehydratase 10 histidinol phosphate aminotransferase 11 histidinol phosphatase 12 histidinol dehydrogenase 

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