Repression of maleate cis-trans isomerase(maleate isomerase) by carbon sources and its reversal were investigated by using Alcaligenes faecalis IB-14.
The formation of maleate isomerase was induced by malonate favorably in a poormedium, whereas it was repressed in a rich medium by carbon sources such as intermediates of TCA cycle. The repression provoked by DL-malate was accompanied with remarkable promotion of the cell growth and with accumulation of a large amount of pyruvate. The enzyme levels of TCA cycle were elevated several times in the DL-malate repressed cells. It was probable to assume that the formation of maleate isomerase was subject to catabolite repression when a rapid and surplus metabolism of DL-malate via TCA cycle was conducted.
So, as an approach to reveal the chemical nature of the catabolite moiety, reversal of the catabolite repression was studied. It was demonstrated that the repression provoked by DL-malate was reversed by various cultural conditions as follows; addition of higher concentrations of malonate, divided supply of DL-malate, “anaerobic” incubation and addition of higher concentrations of ammonium ion. From physiological significances of these events, it was revealed that catabolite repression of maleate isomerase was reversed by minimizing the functioning of TCA cycle.