ACETYL-COA CARBOXYLASE ACTIVITY IN HELICOBACTER-PYLORI AND THE REQUIREMENT OF INCREASED CO2 FOR GROWTH

A biotinylated acetyl-CoA carboxylase from the microaerophilic bacteri um Helicobacter pylori was partially purified and characterized. The a pproximate molecular mass of the native enzyme was estimated at 235 kD a by native PAGE. A single band corresponding to approximately 24 kDa was detected by SDS-PAGE, suggesting that the native enzyme is a multi -protein complex. The protein was isolated from the soluble fraction o f the cell. Catalytic activity was acetyl-CoA-dependent and inhibited by avidin but unaffected by avidin pretreated with excess biotin. The end-product of the reaction was identified as malonyl-CoA and the reac tion was shown to be reversible by NMR spectroscopy. The activity of t he enzyme was 0.29 mu mol min(-1) (mg protein)(-1). The V-max for bica rbonate was calculated at 0.73 mu mol min(-1) (mg protein)(-1), and th e affinity of the enzyme for this substrate was relatively low, with a n apparent K-m of 16.6 mM. These data provide the first evidence of a possible physiological role for the requirement of high levels of CO2 for growth in vitro of this bacterium.