Figure 1.

Catabolic pathway of L-ascorbate in R. eutropha occurs in three modules (A-C) that are encoded in distinct gene clusters (D). A) Module 1: L-Ascorbate is oxidized and hydrolyzed to 2,3-diketo-L-gulonate. B) Module 2: 2,3-diketo-L-gulonate is substrate for a benzilic acid rearrangement to yield 2-carboxy-L-lyxonolactone, which is ring-opened to 2-carboxy-L-lyxonate. C) Module 3: 2-carboxy-L-lyxonate is decarboxylated via oxidation and reduction of C3 to produce L-lyxonate, which is dehydrated twice and oxidized to generate α-ketoglutarate, a citric acid cycle intermediate. D) Gene neighborhood diagrams mentioned in the main text.