Synthesis of (14C)-ribose-5-phosphate and (14C)-phosphoribosylpyrophosphate and their use in new enzyme assays

Biochemical characterization of the Mycobacterium tuberculosis phosphoribosyl-1-pyrophosphate synthetase

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 utilize decaprenol-1-monophosphorabinose as a substrate. 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 pyrimidine biosyntheses. In M. tuberculosis, a single pRpp synthetase enzyme (Mt-PrsA) is solely responsible for the generation of pRpp, by catalyzing 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.

Enzymatic coupled assay procedures that employ high-performance liquid chromatography: the synthesis of orotidylate from ribose

High-performance liquid chromatographic assay procedures have been designed to monitor the catalytic activities of ribokinase and phosphoribosyl alpha-1-pyrophosphate (PRibPP) synthetase. These methods are only of qualitative value, when crude protein extracts are to be examined, because of the presence of myokinase. However, the product of the PRibPP synthetase reaction, can be detected quantitatively even in crude protein extracts through the addition of two enzymes (orotate phosphoribosyltransferase and inorganic pyrophosphatase) that catalyze the conversion of PRibPP into a spectroscopically detectable nucleotide product (orotidylate).