Biochemical characterisation of the Mycobacterium tuberculosis phosphoribosyl-1-pyrophosphate synthetase (Mt-PrsA).

Mycobacterium tuberculosis arabinogalactan (AG) is an essential cell wall component. It provides a molecular framework serving to connect peptidoglycan to the outer mycolic acid layer. The biosynthesis of the arabinan domains of AG and lipoarabinomannan (LAM), occurs via a combination of membrane bound arabinofuranosyltransferases, all of which utilise decaprenol-1-monophosphorabinose as a substrate (DPA). The source of arabinose ultimately destined for deposition into cell wall AG or LAM, originates exclusively from phosphoribosyl-1-pyrophosphate (pRpp), a central metabolite which is also required for other essential metabolic processes, such as de novo purine and pyrimidne biosynthesis. In M. tuberculosis, a single pRpp synthetase enzyme (Mt-PrsA) is soley responsible for the generation of pRpp, by catalysing the transfer of pyrophosphate from ATP to the C1 hydroxyl position of ribose-5-phosphate. Here, we report a detailed biochemical and biophysical study of Mt-PrsA, which exhibits the most rapid enzyme kinetics reported for a pRpp synthetase.