Investigation of 1-deoxy-D-xylulose 5-phosphate synthase and transketolase of Bacillus subtilis in relation to vitamin B6 biosynthesis.

In Escherichia coli, 4-(phosphohydroxy)-L-threonine and 1-deoxy-D-xylulose 5-phosphate are believed to be direct precursors of vitamin B6 (B6), and 1-deoxy-D-xylulose 5-phosphate synthase (Dxs) and transketolase could catalyze the formation of each precursor. In this report, the possible involvement Dxs and transketolase (Tkt) in B6 biosynthesis in Bacillus subtilis was investigated. The gene disruptant of tkt and conditional mutants of dxs were constructed, and their ability of B6 biosynthesis was examined. It was found that the tkt disruptants retain the ability to synthesize B6. The conditional mutant of dxs synthesized the same amount of B6 per dry cell weight as the wild-type strain. Therefore, it is very likely that neither Dxs nor transketolase is involved in B6 biosynthesis in B. subtilis.