5-Keto-d-Fructose: Formation and Utilization in the Course ofd-Fructose Assimilation byGluconabacter cerinus

Publisher Website
Google Scholar
Abstract
The accumulation of 5-keto-d-fructose (5KF) byGluconobacter cerinusgrown ond-fructose in unbuffered medium was shown to be optimal at pH 4.0 after cell growth ceased. During the exponential phase of growth or at neutral pH after the onset of the stationary phase, 5KF production continued but did not accumulate because of its rapid reutilization by reduction tod-fructose. The extent of isotope incorporation into C5 of ribonucleic acid ribose when cells were grown in the presence of specifically labeledd-glucose andd-fructose clearly indicated that (i) the hexose monophosphate oxidative pathway is the predominant metabolic route for carbohydrate assimilation and (ii) extensive randomization of label between C1 and C6 ofd-fructose occurred prior to its conversion into pentose. It is suggested that the cyclic oxidation and reduction through the symmetrical 5KF molecule, which accounts for the observed randomization of isotope ind-fructose, provides the cells with an effective mechanism for the regeneration of nicotinamide adenine dinucleotide phosphate during the period of intensive growth.