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M DOUDOROFF

Publications and source records attributed to M DOUDOROFF.

At least 19 recordsLinked to original sources
PubMed1965

COFACTOR-DEPENDENT ALDOSE DEHYDROGENASE OF RHODOPSEUDOMONAS SPHEROIDES.

Niederpruem, Donald J. (University of California, Berkeley), and Michael Doudoroff. Cofactor-dependent aldose dehydrogenase of Rhodopseudomonas spheroides. J. Bacteriol. 89:697-705. 1965.-Particulate enzyme preparations of cell extracts of Rhodopseudomonas spheroides possess constitutive dehydrogenase and oxidase activities for aldose sugars, reduced nicotinamide adenine dinucleotide (NADH(2)), and succinate. The dehydrogenation of aldoses requires an unidentified cofactor which is not required for the oxidation of succinate nor of NADH(2). The cofactor is present in the particulate fraction of aerobic cells, but is unavailable to the enzyme system. It can be liberated by boiling or by treatment with salts at high concentration. The cofactor also appears in the soluble fraction of aerobic cells, but only after exponential growth has ceased. Extracts of cells grown anaerobically in the light possess the apoenzyme, but not the cofactor, for aldose oxidation. Cofactor activity was found in extracts of Bacterium anitratum (= Moraxella sp.) but not in Escherichia coli, Pseudomonas fluorescens, yeast, or mouse liver. In 0.075 m tris(hydroxymethyl)aminomethane-phosphoric acid buffer (pH 7.3), the oxidation of NADH(2) was stimulated and succinoxidase was inhibited by high salt concentrations.

Alcohol Oxidoreductases↗
PubMed1964

DEPOLYMERIZATION OF POLY-BETA-HYDROXYBUTYRATE BY INTRACELLULAR ENZYME SYSTEM.

Merrick, J. M. (State University of New York, Buffalo), and M. Doudoroff. Depolymerization of poly-beta-hydroxybutyrate by an intracellular enzyme system. J. Bacteriol. 88:60-71. 1964.-The poly-beta-hydroxybutyric acid contained in the "lipid granules" of Bacillus megaterium is hydrolyzed to d(-)-beta-hydroxybutyric acid by a complex enzyme system present in the soluble enzyme fraction of polymer-depleted cells of Rhodospirillum rubrum. This system consists of a thermostable "activator," a thermolabile "depolymerase," and an "esterase." Under certain conditions, the activator can be replaced by trypsin. Various chemical and physical treatments inactivate the "native lipid granules," and make them unsuitable as a substrate for the digestive enzymes. This inactivation of the granules is often expressed in the extent rather than the rate of their digestion, and is not correlated with the destruction of the polymer-synthesizing enzymes associated with the granules. The principal product of depolymerase action is d(-)-beta-hydroxybutyric acid, but small amounts of esterified products are also released. These are hydrolyzed by the esterase.

Bacillus megaterium↗