Effects of 6-O-Methylglucose-Containing Lipopolysaccharides on the Activity of Fatty Acid Elongation Systems in Mycobacterium Smeamatis
Among four species of 6-O-methylglucose-containing lipopolysaccharides (MGLP)1,2) of Mycobacterium smegmatis, MGLP-I, which lacks succinyl residues, and MGLP-II, which contains one mol of succinyl residue per mol of MGLP, inhibited the activity of the acyl carrier protein (ACP)-dependent fatty acid elongation system (FAS-II)3) prepared from the same bacilli by ammonium sulfate precipitations and gel filtration of Sephacryl S-200. When the molar ratio of palmitoyl-CoA to MGLP-II was 1:1, the FAS-II activity was reduced to about 70% of the normal value. When it was 1:3, the activity was about 30%. MGLP-I, on the other hand, inhibited the activity of partially purified palmitoyl-CoA -ACP transacylase, which is one of enzymes of FAS-II. In addition, it also inhibited the activity of the acetyl-CoA-dependent fatty acid elongation system (FES-I)4) when the concentration of decanoyl-CoA used as the optimum primer was lower than its 2 Km value and the activity of the malonyl-CoA-dependent fatty acid elongation system (FES-II)5) when the concentration of stearoyl-CoA used as optimum primer was lower than 50μ-M (the standard concentration of the original assay). The physiological role of these lipopolysaccharides on the mycobacterial lipid metabolism was discussed.