HisB


The hisB gene, found in the enterobacteria, in Campylobacter jejuni and in Xylella/Xanthomonas encodes a protein involved in catalysis of two step in histidine biosynthesis, namely the bifunctional Imidazoleglycerol-phosphate dehydratase/histidinol-phosphatase.
The former function, found at the N-terminal, dehydrated d-erythroimidazoleglycerolphosphate to imidazoleacetolphosphate, the latter function, found at the C-terminal, dephosphorylates l-histidinolphosphate producing histidinol.
The firth step is catalysed instead by histadinolphosphate aminotransferase
The peptide is 40.5kDa and associates to form a hexamer
In E. coli hisB is found on the hisGDCBHAFI operon
The phosphatase activity possess a substrate ambiguity and overexpression of hisB can rescue phosphoserine phosphatase knockouts.

Reactions

hisB-N
hisB-C

Non-fusion protein in other species

from Saccharomyces cerevisiae is not a fused IGP dehydratase and hisidinol phosphatase, but an IGPD only. Whereas HIS2 is the HP.