Regulation of acetate and acetyl-CoA converting enzymes during growth on acetate and/or glucose in the halophilic archaeon Haloarcula marismortui.

Haloarcula marismortui formed acetate during aerobic growth on glucose and utilized acetate as growth substrate. On glucose/acetate mixtures diauxic growth was observed with glucose as the preferred substrate. Regulation of enzyme activities, related to glucose and acetate metabolism was analyzed. It was found that both glucose dehydrogenase (GDH) and ADP-forming acetyl-CoA synthetase (ACD) were upregulated during periods of glucose consumption and acetate formation, whereas both AMP-forming acetyl-CoA synthetase (ACS) and malate synthase (MS) were downregulated. Conversely, upregulation of ACS and MS and downregulation of ACD and GDH were observed during periods of acetate consumption. MS was also upregulated during growth on peptides in the absence of acetate. From the data we conclude that a glucose-inducible ACD catalyzes acetate formation whereas acetate activation is catalyzed by an acetate-inducible ACS; both ACS and MS are apparently induced by acetate and repressed by glucose.