Probably catalyzes the hydrolysis of L-ascorbate-6-P into 3-keto-L-gulonate-6-P. Is essential for L-ascorbate utilization under anaerobic conditions. H2O + L-ascorbate 6-phosphate = 3-dehydro-L-gulonate 6-phosphate Cofactor degradation; L-ascorbate degradation; D-xylulose 5-phosphate from L-ascorbate: step 1/4. Induced by L-ascorbate. Repressed by UlaR. Belongs to the UlaG family.