Abstract
The conversion of methylmalonate semialdehyde to propionyl coenzyme A has been investigated with enzyme preparations made from Pseudomonas aeruginosa grown on valine. A protein fraction has been obtained which catalyzes the oxidation of methylmalonate semialdehyde, acetaldehyde, and propionaldehyde with NAD as the electron acceptor. The product of methylmalonate semialdehyde oxidation in the presence of CoA is heat stable, reacts with hydroxylamine to form propionohydroxamate, is eluted from a chromatographic column of Dowex 1 in the same position as propionyl-CoA, and therefore, appears to be propionyl-CoA. The product of propionaldehyde oxidation in the presence of CoA also has been characterized as propionyl-CoA since it is heat stable and reacts with hydroxylamine to form propionohydroxamate. Oxidation of methylmalonate semialdehyde and propionaldehyde is accompanied by the formation of equal amounts of NADH and an active acyl compound, the latter estimated as the hydroxamate. When CoA is omitted from the reaction mixture, high levels of mercaptoethanol will restore enzyme activity, but catalytic activity is altered. In the presence of CoA, the pH activity curve for the oxidation of methylmalonate semialdehyde is much broader and the specific activity of the enzyme is higher than when CoA is absent. Omission of CoA from reaction mixtures has little effect on the pH activity curve for the oxidation of propionaldehyde however. Other enzymes concerned with propionyl-CoA metabolism which have been identified in extracts of P. aeruginosa are phosphotransacetylase, propionyl-CoA carboxylase, and lactyl-CoA dehydrase.
Highlights
The conversion of methyhnalonate semialdehyde to propionyl coenzyme A has been investigated with enzyme preparations made from Pseudomonas aeruginosa grown on valine
The standard assay was used to measure the activity of unfractionated extracts toward methylmalonate semialdehyde and propionaldehyde, provided the rate of NADH formation was less than 10 mpmoles per min
No enzyme was detected in extracts prepared from cells of P. aeruginosa grown on glucose when they were assayed with methylmalonate semialdehyde aerobically or anaerobically using Thunberg cuvettes
Summary
The conversion of methyhnalonate semialdehyde to propionyl coenzyme A has been investigated with enzyme preparations made from Pseudomonas aeruginosa grown on valine. The product of methyhnalonate semialdehyde oxidation in the presence of CoA is heat stable, reacts with hydroxylamine to form propionohydroxamate, is eluted from a chromatographic column of Dowex 1 in the same position as propionyl-. The product of propionaldehyde oxidation in the presence of CoA has been characterized as propionyl-CoA since it is heat stable and reacts with hydroxylamine to form propionohyfound that rats which were fed L-valine-I-r3C produced glycogen labeled in positions 1, 2, 5, and 6 of glucose. This labeling pattern was identical with that obtained by Lorber et al (2) when they fed propionate labeled in position 2 or 3 to rats, and it led Peterson et al to propose that the a-carbon fragment produced from valine was propionate.
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