T. Mizote et al., THE THIJ LOCUS AND ITS RELATION TO PHOSPHORYLATION OF HYDROXYMETHYLPYRIMIDINE IN ESCHERICHIA-COLI, Microbiology, 142, 1996, pp. 2969-2974
Extracts from Escherichia coli K-12 contained two distinct enzymes cap
able of catalysing the phosphorylation of hydroxymethylpyrimidine (HMP
) to HMP monophosphate: pyridoxine kinase (EC 2.7.1.35) and an enzyme
that has not previously been genetically analysed, HMP kinase (EC 2.7.
1.49). Two distinct genes, pdxL and thiJ, specify the activities of th
e former and latter enzymes, respectively; The inactivation of both ge
nes by independent mutations in the same cell resulted in the complete
loss of HMP kinase activity. Experiments with a series of strains tha
t carry mutations in thiC, thiC pdxB, thiC pdxB pdxL and thiC pdxB pdx
L thiJ revealed that the ability of the double mutant (pdxL thiJ) to u
tilize HMP in thiamin pyrophosphate biosynthesis was restored by intro
ducing the wild-type allele corresponding to the thiJ mutation. The th
iJ locus was mapped on the chromosome near the thiD and thiM loci, whi
ch govern the activities of phosphomethylpyrimidine kinase (EC 2.7.4.7
) and hydroxyethylthiazole kinase (EC 2.7.1.50), respectively.