In vitro characterization of alternative L-threonate and D-erythronate catabolic pathways

L-threonate is the metabolite of vitamin C, while D-erythronate is the metabolite of N-acetyl-D-glucosamine, the nutritional supplement for joint health. They are widely distributed in the environment and human biofluids. Nevertheless, the catabolisms of L-threonate and D-erythronate are sparsely reported. Here we explored the functional diversity of an acid sugar kinase family (Pfam families PF07005-PF17042), and discovered a novel 2oxo-tetronate kinase. The conserved genome neighborhood of the 2-oxo-tetronate kinase encodes members of class-II fructose-bisphosphate aldolase family (F_bP_aldolase, PF01116) and a dehydrogenase family (PF03446PF14833). Instructed by this analysis, we experimentally verified that these enzymes are capable of degrading Lthreonate into dihydroxyacetone phosphate (DHAP) in Arthrobacter sp. ZBG10, Clostridium scindens ATCC 35704, and Pseudonocardia dioxanivorans ATCC 55486. Meanwhile, a convergent catabolic pathway for D-erythronate was characterized in P. dioxanivorans ATCC 55486. Moreover, the phylogenetic distribution analysis indicates that the biological range of the identified L-threonate and D-erythronate catabolic pathways appears to extend mostly to members of the Actinomycetota, Cyanobacteriota, Bacillota, Pseudomonadota, and Bacteroidota phyla.