Biochemical aspects of 2-keto-L-gulonate accumulation from 2,5-diketo-D-gluconate by Corynebacterium sp. and its mutants.

Abstract

Corynebacterium sp. SHS 0007 accumulated 2-keto-L-gulonate and 2-keto-D-gluconate simultaneously with 2, 5-diketo-D-gluconate utilization. This strain, however, possibly metabolized 2, 5-diketo-D-gluconate through two pathways leading to D-gluconate as a common intermediate: via 2-keto-D-gluconate, and via 2-keto-L-gulonate, L-idonate and 5-keto-D-gluconate. A polysaccharidenegative, 2-keto-L-gulonate-negative and 5-keto-D-gluconate-negative mutant produced only calcium 2-keto-L-gulonate from calcium 2, 5-diketo-D-gluconate, in a 90.5mol% yield. The addition of a hydrogen donor such as D-glucose was essential for its production. This mutant possessed the direct oxidation route of D-glucose to D-gluconate, the pentose cycle pathway and a possible Embden-Meyerhof-Parnas pathway, indicating that D-glucose was metabolized through these three pathways and provided NADPH for the reduction of 2, 5-diketo-D-gluconate.