Cloning and expression of the trehalose-phosphate phosphatase of Mycobacterium tuberculosis: comparison to the enzyme from Mycobacterium smegmatis

Abstract

Two open reading frames in the Mycobacterium tuberculosis genome, Rv3372 and Rv2006, have about 25% sequence identity at the amino acid level to the trehalose-phosphate phosphatase (TPP) purified from Mycobacterium smegmatis. However, the protein produced from the cloned Rv3372 gene has a molecular weight of about 45 kDa whereas the trehalose-P phosphatase purified from M. smegmatis has a molecular weight of about 27 kDa. We expressed the Rv3372 protein in Escherichia coli and show here that it is a trehalose-P phosphatase with very similar properties to the M. smegmatis TPP, i.e., complete specificity for trehalose-phosphate as the substrate, an almost absolute requirement for Mg 2+, and a pH optimum of 7–7.5. On the other hand, in contrast to the M. smegmatis enzyme, the Rv3372 protein was much less stable to heat and much less sensitive to inhibition by diumycin and moenomycin. In fact, both of these antibiotics stimulate enzyme activity at low concentrations and only inhibit the activity at higher antibiotic concentrations. Antibody prepared against the 27 kDa TPP does not cross react with the 45 kDa TPP nor does antibody against the 45 kDa TPP cross react with the 27 kDa TPP. Nevertheless, studies of secondary structure by circular dichroism indicate that the two enzymes are quite similar in structure. The product of the other gene, Rv2006, is a 159 kDa protein with no detectable phosphatase activity. Thus, its function is currently unknown.