Lipoate metabolism in Pseudomonas putida LP

Abstract

dl-[1,6- 14C]Lipoate was used to support the growth of Pseudomonas putida LP, which was found to grow on d- or l-lipoate as sole source of carbon and sulfur. The major radioactive catabolite in the benzene extract from acidified aerobic cultures was identified to be bisnorlipoate. The principal acidic 14C-catabolites in the aqueous phase have now been isolated and identified as β-hydroxybisnorlipoate, as well as bisnorlipoate; the existence of lesser amounts of tetranorlipoate is also indicated by Chromatographic evidence. Although the microorganism can grow on 8-methyllipoate (6,8-dithiononanoate), the bisnor- and tetranor-compounds, as well as 6,9-dithiononanoate (a dithiane derivative), do not support growth. Hence, the bacterium can derive most of the needed carbon by β-oxidation of the acid side chain of a 3-substituted dithiolane to yield the two-carbon-shorter bisnor-compound. Less extensive degradation of bisnorlipoate results in the formation of β-hydroxybisnorlipoate, which may be further metabolized to tetranorlipoate.