Studies of Isocitrate Dehydrogenase From Bacillus caldotenax

Most micro-organisms contain an NADP-dependent isocitrate dehydrogenase (ICDH) activity. During growth of micro-organisms on acetate as the sole carbon source the two enzymes of the glyoxylate bypass, isocitrate lyase (ICL) and malate synthase (MS), are induced. These two enzymes are required to generate the intermediates of the TCA cycle that are used for biosynthesis. Under these conditions there is competition between the TCA cycle enzyme ICDH and the glyoxylate bypass enzyme ICL for available isocitrate. In E. coli this competition is overcome by the partial phosphorylation and inactivation of ICDH. This mechanism of control has been observed in other enteric bacteria