Characterization of the Growth of Pseudomonas Putida LP on Lipoate and its Analogues: Transport, Oxidation, Sulphur Source, and Enzyme Induction

Abstract

S U M M A R YPseudomonas putida LP, which grows on lipoate, NH,NO, and mineral salts, converts most of the organic substrate to bisnor-lipoate (I ,2-dithiolane-3-propanoic acid) and acetyl-CoA. D-, L-, or ~~-1 i p o a t e serve equally well as carbon and sulphur sources. There was no growth on or bacterial oxidation of the chemicalIy synthesized bisnor-or tetranor-( I ,2-dithiolane-3-carboxylic acid) chain-shortened analogues, but these, as well as lipoate, could supply the sulphur needed for growth when acetate was provided as the sole source of carbon. The uptake of lipoate by the bacterium is very slow and non-inducible, while the uptake of acetate is faster than octanoate. The oxidation of octanoate is more rapid and extensive than that of lipoate. Levels of acyl-CoA synthetase are not affected by the source of carbon, but activities of isocitrate lyase and malate synthase are higher when the cells are grown in acetate, octanoate or lipoate and lower when glucose is the carbon source. The glyoxylate cycle is induced to facilitate utilization of acetyl-CoA derived from lipoate, which is also degraded to water-soluble catabolites that yield the much smaller amount of sulphur required for growth. I N T R O D U C T I O NAlthough the principal biochemical function of lipoic (thioctic) acid in a-keto acid dehydrogenases is understood, little was known concerning the metabolic fate of this compound. An organism identified as Pseudomonasputida LP was isolated and adapted to grow in a synthetic medium, which contained 0.4 % (w/v) lipoic acid as the sole source of carbon, sulphur and energy. One major catabolite was identified as bisnor-lipoic (I ,a-dithiolane-3-propanoic) acid, indicating at least partial P-oxidation of the side chain (Shih, Wright & McCormick, I 972).We have now studied uptake, oxidation and sulphur utilization of lipoic acid and its chainshortened analogues by this lipoate-degrading pseudomonad. To ascertain the existence of pathways for P-oxidation and the glyoxylate cycle in the pseudomonad grown on lipoate, some relevant enzyme activities have also been determined.

Micronutrient cofactor research with extensions to applications

“…Though side-chain β-oxidation and S oxidation occur in bacteria and mammals, extensive degradation of the bicyclic ring system is known to occur only in certain bacteria. ment culture from soil (Shih et al 1972(Shih et al , 1975Chang et al 1975;, and then in the rat (Harrison & McCormick, 1974;Spence & McCormick, 1976). Syntheses and delineation of the properties of critical side-chain-shortened catabolites, for example bisnor-and tetranorlipoates, were also accomplished (Shih et al 1974) as were HPLC chromatographic separations of metabolites (Howard & McCormick, 1981).…”

A Trail of Research on Cofactors: An Odyssey with Friends

“…Similar studies on the catabolic fate of lipoate were conducted. We detailed total degradation in a pseudomonad (Chang et al 1975, Shih et al 1972, Shih et al 1975 and in the rat (Harrison andMcCormick 1974, Spence and. Synthesis and delineation of the properties of critical side-chain shortened metabolites were also accomplished (Shih et al 1974) as were HPLC chromatographic separations of metabolites (Howard and McCormick 1981).…”