Phosphotransbutyrylase expression in Bacillus megaterium

The molecular analysis of a genomic region of B. megaterium revealed the pr esence of a gene coding for the enzyme phosphotransbutyrylase (Ptb). The en zyme activity was measured throughout the different phases of growth in B. megaterium, and its activity was found to be maximal in the late exponentia l growth phase. The branched amino acids isoleucine and valine activated Pt b expression. Ptb(Bm) was capable of using butyryl-CoA and 2-methyl-propion yl CoA as substrates. Act(Bm), a sigma (54) regulator from B. megaterium wh ose gene is situated upstream from the ptb gene, activated its expression.