Biosynthesis of D‐arabinose in mycobacteria – a novel bacterial pathway with implications for antimycobacterial therapy

Abstract

Decaprenyl-phospho-arabinose (b-d-arabinofuranosyl-1-O-monophosphodecaprenol), the only known donor of d-arabinose in bacteria, and its precursor, decaprenyl-phospho-ribose (b-d-ribofuranosyl-1-O-monophosphodecaprenol), were first described in 1992. En route to d-arabinofuranose, the decaprenyl-phospho-ribose 2¢-epimerase converts decaprenyl-phospho-ribose to decaprenyl-phospho-arabinose, which is a substrate for arabinosyltransferases in the synthesis of the cell-wall arabinogalactan and lipoarabinomannan polysaccharides of mycobacteria. The first step of the proposed decaprenylphospho-arabinose biosynthesis pathway in Mycobacterium tuberculosis and related actinobacteria is the formation of d-ribose 5-phosphate from sedoheptulose 7-phosphate, catalysed by the Rv1449 transketolase, and ⁄ or the isomerization of d-ribulose 5-phosphate, catalysed by the Rv2465 d-ribose 5-phosphate isomerase. d-Ribose 5-phosphate is a substrate for the Rv1017 phosphoribosyl pyrophosphate synthetase which forms 5-phosphoribosyl 1-pyrophosphate (PRPP). The activated 5-phosphoribofuranosyl residue of PRPP is transferred by the Rv3806 5-phosphoribosyltransferase to decaprenyl phosphate, thus forming 5¢-phosphoribosyl-monophospho-decaprenol. The dephosphorylation of 5¢-phosphoribosyl-monophospho-decaprenol to decaprenyl-phospho-ribose by the putative Rv3807 phospholipid phosphatase is the committed step of the pathway. A subsequent 2¢-epimerization of decaprenyl-phospho-ribose by the heteromeric Rv3790 ⁄ Rv3791 2¢-epimerase leads to the formation of the decaprenyl-phospho-arabinose precursor for the synthesis of the cell-wall arabinans in Actinomycetales. The mycobacterial 2¢-epimerase Rv3790 subunit is similar to the fungal d-arabinono-1,4-lactone oxidase, the last enzyme in the biosynthesis of d-erythroascorbic acid, thus pointing to an evolutionary link between the d-arabinofuranose-and l-ascorbic acidrelated pathways. Decaprenyl-phospho-arabinose has been a lead compound for the chemical synthesis of substrates for mycobacterial arabinosyltransferases and of new inhibitors and potential antituberculosis drugs. The peculiar (x,mono-E,octa-Z) configuration of decaprenol has yielded insights into lipid biosynthesis, and has led to the identification of the novel Z-polyprenyl diphosphate synthases of mycobacteria. Mass spectrometric methods were developed for the analysis of anomeric linkages and of dolichol phosphaterelated lipids. In the field of immunology, the renaissance in mycobacterial polyisoprenoid research has led to the identification of mimetic mannosyl-b-1-phosphomycoketides of pathogenic mycobacteria as potent lipid antigens presented by CD1c proteins to human T cells.Abbreviations ALO, D-arabinono-1,4-lactone oxidase; Araf, D-arabinofuranose; GLO, L-gulono-1,4-lactone oxidase; PRPP, 5-phosphoribosyl 1-pyrophosphate.

Determinants of the Inhibition of DprE1 and CYP2C9 by Antitubercular Thiophenes

“…Mtb Decaprenylphosphoryl‐β‐ d ‐ribofuranose 2‐oxidase (DprE1) is a flavin adenine dinucleotide (FAD)‐dependent enzyme, which together with decaprenylphosphoryl‐ d ‐2‐ketoerythropentose reductase (DprE2), converts decaprenylphosphoryl‐beta‐ d ‐ribose (DPR) to decaprenylphosphoryl‐beta‐ d ‐arabinofuranose (DPA), an essential cell wall component 1. Conditional knockdown studies showed that loss of dprE1 results in a strong bactericidal effect in vitro 2.…”

Prokaryotic Expression, Identification and Bioinformatics Analysis of the Mycobacterium tuberculosis Rv3807c Gene Encoding the Putative Enzyme Committed to Decaprenylphosphoryl-d-arabinose Synthesis

“…However, the phospholipid phosphatase involved has not been identified yet. The presence of an unknown PAP2-family phospholipid phosphatase (Rv3807c) located next to the phosphoribosyltransferase (Rv3806c) was predicted to catalyze the reaction of dephosphorylation [11]. In this study, we constructed the recombinant plasmid pColdII-Rv3807c to clone and express the Rv3807c gene and identified the localization, functional and structural characteristics of the Rv3807c protein to enable further confirmatory study on the relationship between Rv3807c and DPA biosynthesis.…”

“…Ethambutol, a first-line drug for treatment of TB with pleiotropic effects, however, does not block the synthesis of DPA [11], which directly influence AG biosynthesis, even the formation of the cell wall in mycobacterium [10,17]. It remains to be determined whether the speculated enzyme Rv3807c catalyses the conversion of DPPR to DPR and its precise role in the biosynthesis of DPA.…”

“…Subsequently, the 5-phosphate unit is removed from 5-phospho-decaprenylphospho-ribose to form decaprenyl-phosphoryl-ribose (DPR) by the putative Rv3807 phospholipid phosphatase [10,11]. The final step of the biosynthetic pathway of decaprenyl-phospho-arabinose is the 2 0 -epimerization from DPR to DPA, catalyzed by the heteromeric Rv3970/Rv3971 2 0 -epimerase which is probably not released from the mycobacterial enzyme under physiological conditions [12,13].…”

“…However, the biological function of the Rv3807 gene product, as a good candidate of a specific decaprenyl-phospho-ribose-5 0 -phosphate phosphatase, which is located next to the phosphoribosyltransferase (Rv3806c), has not been accurately elucidated yet. The upstream Rv3806c is reversible in the absence of pyrophosphatase activity, therefore the phosphatase reaction is expected to be irreversible [11]. It is necessary to identify the phospholipid phosphatase (Rv3807c) and to accomplish the mechanism of biosynthesis of decaprenyl-phospho-arabinose in mycobacteria.…”