The Mycobacterium tuberculosis Rv1099c gene encodes a GlpX-like class II fructose 1,6-bisphosphatase.

There are now abundant data indicating that Mycobacterium tuberculosis uses fatty acids as a carbon source in vivo. A key enzyme in gluconeogenesis, missing in the original annotation of the M. tuberculosis genome, is fructose 1,6-bisphosphatase (FBPase; EC 3.1.3.11). The authors have shown that M. tuberculosis Rv1099c, a glpX homologue, can complement Escherichia coli mutants lacking FBPase. The protein encoded by Rv1099c was shown to have FBPase activity. Rv1099c was expressed at significant levels in M. tuberculosis, and may encode the major FBPase of this pathogen.