Search PubMed⌕ Search

Biomedical subjects

S Englard

Publications and source records attributed to S Englard.

At least 37 records · Page 2Linked to original sources
PubMed1978

A simplified method for the measurement of gamma-butyrobetaine hydroxylase activity.

A method for the assay of gamma-butyrobetaine hydroxylase activity is described. The procedure is based on the measurement of 3H2O formed from [2,3-3H]gamma-butyrobetaine. The formation of 3H2O was essentially linear with time of incubation and enzyme concentration. Despite a significant isotope effect that causes the extent of hydroxylation to be underestimated, an appropriately determined correction factor permits one to relate quantitatively the degree of detritiation to the amount of carnitine formed. The assay is simple, rapid, specific, accurate, highly reproducible, and relatively sensitive. Its reliability and convenience represent an improvement over existing methods based on the tedious and time-consuming enzymatic radioisotopic determination of the carnitine formed or on the coupled decarboxylation of [1-14C]alpha-ketoglutarate, a method that cannot be used in crude extracts.

Animals↗
PubMed1974

5-Keto-D-fructose: formation and utilization in the course of D-fructose as similation by Gluconabacter cerinus.

The accumulation of 5-keto-d-fructose (5KF) by Gluconobacter cerinus grown on d-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 to d-fructose. The extent of isotope incorporation into C5 of ribonucleic acid ribose when cells were grown in the presence of specifically labeled d-glucose and d-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 of d-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 in d-fructose, provides the cells with an effective mechanism for the regeneration of nicotinamide adenine dinucleotide phosphate during the period of intensive growth.

Bacteria↗
PubMed1974

Metabolic consequences of a block in the synthesis of 5-keto-D-fructose in a mutant of Gluconobacter cerinus.

A mutant of Gluconobacter cerinus var. ammoniacus, IFO 3267, has been isolated which is deficient with respect to fructose 5-dehydrogenase, the enzyme catalyzing the oxidation of d-fructose to 5-keto-d-fructose (5 KF). Growth of this mutant on fructose as the sole carbon source was impaired unless the culture medium was supplemented with 5 KF. Significant randomization of the 1 and 6 positions of fructose has been reported previously for the wild-type organism during growth on this ketohexose. The pattern of (3)H incorporation into the C5 position of ribonucleic acid-ribose when the mutant was grown on [1-(3)H]fructose and [6-(3)H]fructose in the presence of 5 KF indicated that such randomization did not occur in this variant. The randomization observed in the wild type is, therefore, a consequence of the partial oxidation of fructose to the symmetrical 5 KF intermediate prior to its conversion to pentose. When the mutant was grown on [1-(3)H]fructose in the presence of unlabeled 5 KF, [5-(3)H]fructose appeared in the culture medium. Thus, 5 KF served as the oxidant for the nicotinamide adenine dinucleotide phosphate, reduced form, generated during growth on fructose.

Alcohol Oxidoreductases↗