Histidinol-phosphate aminotransferase

SL-histidinol phosphate aminotransferase histidinol phosphate phosphatase ( histidinol dehydrogenase... 

Fig. 2. The pathway of histidine biosynthesis. Enzymes a, ribosephosphate pyrophos-phokinase E.C. 2.7.6.1 b, ATP-phosphoribosyltransferase, E.C. 2.4.2.17 c, phosphoribosyl-AMP cyclohydrolase, E.C. 3.5.4.19 d, N-(5 -phospho-D-ribosylforminino)5-amino-l-(5"-phos-phoribo yl)-4-imidazole carboxamide isomerase, E.C. 5.3.1.16 e, glutamine amidotransferase f, imidazolglycerolphosphate dehydratase E.C. 4.2.1.19 g, histidinol-phosphate aminotransferase E.C. 2.6.1.9 h, histidinol phosphatase, E.C. 3.1.3.15 i, histidinol dehydrogenase, E.C. 1.1.1.23.

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... 

Fig. 4. Histidine tnosynthess. Intermediates PRPP, phosphoribosyl pyrophosidiate PR-ATP, JV-phoqjhoribosyl-ATP PR-AMP, A/ -phosphoribosyl-AMP PR-FAIC-RN, phosphoribosyl for-mimino-S-amino imidazole carboxamide ribonucleotide PRu-FAIC-RN, phosphoribulosyl for-mimino-5-aniino imidazole carboxamide ribonucleotide IGP, imidazole glycerol phosphate lAP, imidazole acetol idrosphate HP, histidinol (dioqrhate HOL, histidinol. Enzymes (I) ATP phos-phoribosyltransferase (EC 2.4.2.17) (2) phosphoribosyl-ATP pyrophosphohydrolase (EC 3.6.1.31) (3) idiospharibosyl-AMP cyciohydrolase (EC 3.5. A19) (4) PR-FAIC-RN isomerase (EC S.3.1.16) (S) glutamine amidotransferase (6) cyclase (7) imidazole glycerol phosphate dehydratase (EC 4.2.1.19) (8) histidinol-phosphate aminotransferase (EC 2.6.1.9) (9) histidinol phosphatase (EC 3.1.3.15) (10) histidinol dehydrogenase (EC 1.1.1.23).

This pyridoxal-phosphate-dependent enzyme [EC 2.6.1.9], also called imidazolylacetolphosphate aminotransferase and imidazole acetolphosphate transaminase, catalyzes the reversible reaction of histidinol phosphate with a-ketoglutarate (or, 2-oxoglutarate) to produce 3-(imidazol-4-yl)-2-oxopropyl phosphate and glutamate. 

---