Bp. Burns et al., ACETYL-COA CARBOXYLASE ACTIVITY IN HELICOBACTER-PYLORI AND THE REQUIREMENT OF INCREASED CO2 FOR GROWTH, Microbiology, 141, 1995, pp. 3113-3118
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.