l-Sorbose metabolism in Agrobacterium tumefaciens

The pathway of l-sorbose metabolism in Agrobacterium tumefaciens strain B6 was determined to be: l-sorbose d-glucitol (sorbitol) d-fructose d-fructose-6-phosphate d-glucose-6-phosphate. The reduction of l-sorbose and the oxidation of d-glucitol were mediated by NADPH- and NAD⁺-linked oxidoreductases, respectively. The intermediates, d-glucitol and d-fructose, were isolated from in vitro reaction mixtures by column chromatography on Dowex 1-borate, and identified enzymatically. d-Fructose was identified chemically by its ¹H-NMR spectrum and the IR spectrum and the melting point of the fructosazone. d-Glucitol was characterized chemically by the melting point and the IR spectrum of its hexaacetate.A. tumefaciens ICPB TT111, a representative of another genetic race of Agrobacterium, lacked l-sorbose reductase and therefore failed to grow on l-sorbose; it grew normally on d-glucitol.