Catabolism of D-glucose by Pseudomonas putida U occurs via extracellular transformation into D-gluconic acid and induction of a specific gluconate transport system

Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de León, 24007 León, Spain ABSTRACT Pseudomonas putida U does not degrade D-glucose through the glycolytic pathway but requires (i) its oxidation to D -gluconic acid by a peripherally located constitutive glucose dehydrogenase (insensitive to osmotic shock), (ii) accumulation of D -gluconic acid in the extracellular medium, and (iii) the induction of a specific energy-dependent transport system responsible for the uptake of D -gluconic acid. This uptake system showed maximal rates of transport at 30 ° in 50 mM potassium phosphate buffer, pH 7.0. Under these conditions the Km calculated for D -gluconic acid was 6.7 µM. Furthermore, a different transport system, specific for the uptake of glucose, was also identified. It is active and shows maximal uptake rates at 35 ° in 50 mM potassium phosphate buffer, pH 6.0, with a K m value of 8.3 µM. Author for correspondence: José M. Luengo. Tel: +34 87 291226. Fax: +34 87 291226/291194. Keywords: D -glucose, D -gluconic acid, Pseudomonas putida