Component of the DprE1-DprE2 complex that catalyzes the 2-step epimerization of decaprenyl-phospho-ribose (DPR) to decaprenyl-phospho-arabinose (DPA), a key precursor that serves as the arabinose donor required for the synthesis of cell-wall arabinans (PubMed:22188377). DprE1 catalyzes the first step of epimerization, namely FAD-dependent oxidation of the C2' hydroxyl of DPR to yield the keto intermediate decaprenyl-phospho-2'-keto-D-arabinose (DPX) (PubMed:22188377). The intermediate DPX is then transferred to DprE2 subunit of the epimerase complex, most probably through a 'substrate channel' at the interface of DprE1-DprE2 complex (By similarity). Can also use farnesyl-phosphoryl-beta-D-ribofuranose (FPR) as substrate in vitro (PubMed:22188377, PubMed:22956199). Appears to be essential for the growth of M.smegmatis (PubMed:21346818). FAD + H(+) + trans,octa-cis-decaprenylphospho-beta-D-ribofuranose = FADH2 + trans,octa-cis-decaprenylphospho-beta-D-erythro-pentofuranosid-2-ulose Is inhibited by 8-nitro-benzothiazinones (BTZs) such as BTZ043; BTZs are a new class of antimycobacterial agents that block formation of both cell-wall lipoarabinomannan and arabinogalactan via inhibition of decaprenyl-phospho-arabinose (DPA) synthesis (PubMed:19299584, PubMed:22188377). BTZs are suicide inhibitors that act via covalent modification of DprE1; the essential nitro group of these compounds is reduced by DprE1 to a nitroso group, which then specifically reacts with Cys-386 of DprE1 to form an irreversible semimercaptal adduct (PubMed:22188377, PubMed:22956199). Other compounds with diverse scaffolds (dinitrobenzamides and nitrobenzoquinoxalines) also act as covalent DprE1 inhibitors (PubMed:22956199). kcat is 12.7 min(-1) for epimerase activity with FPR as substrate (at pH 8.5 and 25 degrees Celsius). Cell wall biogenesis; cell wall polysaccharide biosynthesis. Monomer (PubMed:22956199). Interacts with DprE2 to form an epimerase complex (By similarity). Disruption of this gene is only possible in the presence of a plasmid-encoded copy of the gene. Curing of this 'rescue' plasmid from the bacterial population results in a cessation of growth, demonstrating gene essentiality. Belongs to the DprE1 family. Extended N-terminus.