The smaller branch consists mainly of phosphatases and phytases with functions ranging from extracellular metabolism to involvement in developmental processes [9, 12]. Examples include human testicular acid phosphatase and lysosomal acid phosphatase [9, 13, 14]. The functions of enzymes in this superfamily are based on a conserved catalytic histidine residue in the motif ‘RHG’ present at the N terminal, which becomes phosphorylated during the reaction [9, 15]. TPCA-1 purchase members of the histidine phosphatase superfamily that have been studied in M. tuberculosis, include Rv0489. The crystal structure of Rv0489 at 1.7 Å resolution reveals the catalytic residues superimposing with those of the cofactor selleck compound library dependent phosphoglycerate mutase
of E. coli, with which it shares 42% amino acid identity [16]. However, its biochemical characteristics remain unknown. Other members include Rv3214c, an acid phosphatase selleckchem with unknown specific substrate [3] and Rv2419c which was characterized as glucosyl-3-phosphoglycerate phosphatase in lipopolysaccharide biosynthesis with an optimum pH of 7.0 [17]. Rv2135c is a paralog of the aforementioned members of the superfamily, but it is annotated as a hypothetical protein in the genomic
database of M. tuberculosis[18]. Bioinformatics similarity searches show that it is a probable cofactor dependent phosphoglycerate mutase. However, there have been reports that proteins annotated as cofactor dependent phosphoglycerate mutases by sequence similarity actually perform the functions of an acid phosphatase when assayed in vitro[9]. Examples in M. tuberculosis are Rv2419c [17] and Rv3214c [3]. In other organisms, examples include PhoE of Bacillus stearothermophillus, and PfPGM2 of Plasmodium falciparum[4, 19]. Rv2135c was GNA12 found in Triton X-114 fractions of M. tuberculosis H37Rv strain and reported as one of the cell envelope associated hypothetical proteins [20]. Rv2135c contains a catalytic histidine
motif similar to proteins in histidine phosphatase superfamily. Nevertheless, its motif is ‘RHA’ unlike ‘RHG’ commonly found in histidine phosphatase superfamily. These motivate the need to investigate its function in the metabolism of M. tuberculosis. Phosphoglycerate mutases (EC 5.4.2.1) primarily interconvert 3-phosphoglyceric acid (3-PGA) and 2-phosphoglyceric acid (2-PGA) in both glycolysis and gluconeogenesis [12, 21]. Two different types of phosphoglycerate mutase have been identified. One depends on the cofactor, 2,3-bisphosphoglyceric acid, for activity (dPGMs) while the other does not (iPGMs) [12, 21]. The cofactor-dependent form is found in vertebrates, budding yeast, and bacterial species, while the cofactor-independent form is the only phosphoglycerate mutase present in higher plants. Some bacteria like E. coli, however, possess both forms [22]. There is no amino acid sequence similarity between these two types of PGMs and their structures are also quite different. Deficiencies in dPGM in E.