Polyprenyl phosphate biosynthesis in Mycobacterium tuberculosis and Myobacterium smegmatis

Mycobacterium smegmatis has been shown to contain two forms of polyprenyl p hosphate (Pol-P), while Mycobacterium tuberculosis contains only one. Utili zing subcellular fractions from M. smegmatis and M. tuberculosis, we show t hat Pol-P synthesis is different in these species. The specific activities of the prenyl diphosphate synthases in M. tuberculosis are 10- to 100-fold lower than those in M. smegmatis. In M. smegmatis decaprenyl diphosphate an d heptaprenyl diphosphate were the main products synthesized in vitro, wher eas in M. tuberculosis only decaprenyl diphosphate was synthesized. The dat a from both organisms suggest that geranyl diphosphate is the allylic subst rate for two distinct prenyl diphosphate synthases, one located in the cell membrane that synthesizes omega,E,Z-farnesyl diphosphate and the other pre sent in the cytosol that synthesizes w,omega,E,E,E-geranylgeranyl diphospha te. In M. smegmatis, the omega,E,Z-farnesyl diphosphate is utilized by a me mbrane-associated prenyl diphosphate synthase activity to generate decapren yl diphosphate, and the omega,E,E,E-geranylgeranyl diphosphate is utilized by a membrane-associated activity for the synthesis of the heptaprenyl diph osphate. In M. tuberculosis, however, omega,E,E,E-geranylgeranyl diphosphat e is not utilized for the synthesis of heptaprenyl diphosphate, Thus, the d ifference in the compositions of the Pol-P of M. smegmatis and M. tuberculo sis can be attributed to distinct enzymatic differences between these two o rganisms.