hisB
The hisB gene, found in the enterobacteria (such as E. coli), in Campylobacter jejuni and in Xylella/Xanthomonas encodes a protein involved in catalysis of two step in histidine biosynthesis (the sixth and eight step), namely the bifunctional Imidazoleglycerol-phosphate dehydratase/histidinol-phosphatase.[1]
The former function (Template:EC number), found at the N-terminal, dehydrated d-erythroimidazoleglycerolphosphate to imidazoleacetolphosphate, the latter function (Template:EC number), found at the C-terminal, dephosphorylates l-histidinolphosphate producing histidinol.[2][3][4]
The firth step is catalysed instead by histadinolphosphate aminotransferase (encoded by hisC)[5]
The peptide is 40.5kDa and associates to form a hexamer (unless truncated)[6]
In E. coli hisB is found on the hisGDCBHAFI operon[7]
The phosphatase activity possess a substrate ambiguity and overexpression of hisB can rescue phosphoserine phosphatase (serB) knockouts.[8]
Reactions
hisB-N
- D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate 3-(imidazol-4-yl)-2-oxopropyl phosphate + H2O
hisB-C
- L-histidinol phosphate + H2O L-histidinol + phosphate
Non-fusion protein in other species
HIS3 from Saccharomyces cerevisiae is not a fused IGP dehydratase and hisidinol phosphatase, but an IGPD only (homologous to hisB-N). Whereas HIS2 is the HP (analogous to hisB-C, called hisJ in some prokaryotes).
References
- ↑ Template:Cite journal
- ↑ Parker95: Parker, A.R., Moore, J.A., Schwab, J.M., Davisson, V.J. (1995). "Escherichia coli Imidazoleglycerol Phosphate Dehydratase: Spectroscopic Characterization of the Enzymic Product and the Steric Course of the Reaction." Journal of the American Chemical Society.
- ↑ Template:Cite journal
- ↑ Template:Cite journal
- ↑ Template:Cite journal
- ↑ Template:Cite journal
- ↑ Template:Cite journal
- ↑ Template:Cite journal