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C Bernofsky

Publications and source records attributed to C Bernofsky.

41 records · Page 3Linked to original sources
PubMed1968

Interconversions of mitochondrial pyridine nucleotides.

Among the factors that can govern the relative rates of mitochondrial oxidation of isocitrate by means of the isocitrate dehydrogenases linked to diphospho-and triphosphopyridine nucleotides are the intramitochondrial concentrations of these nucleotides. Yeast mitochondria contain enzymes that can alter the ratio of these pyridine nucleotides by interconverting them. A diphosphopyridine nucleotide kinase catalyzes the formation of triphosphopyridine nucleotide from diphosphopyridine nucleotide and adenosine triphosphate; a phosphatase converts triphosphopyridine nucleotide to diphosphopyridine nucleotide. Both reactions are more active with the reduced forms of the pyridine nucleotide coenzymes. These studies suggest that the activity of the mitochondrial triphosphopyridine-nucleotide-linked isocitrate dehydrogenase may be regulated by a cyclic system of pyridine-nucleotide interconversions involving triphosphopyridine nucleotide synthesis and breakdown.

Citrates↗
PubMed1966

Diaphorases from Aerobacter aerogenes.

Bernofsky, Carl (The University of Kansas, Kansas City), and Russell C. Mills. Diaphorases from Aerobacter aerogenes. J. Bacteriol. 92:1404-1414. 1966.-Five enzymes which catalyze the reduction of 2,6-dichlorophenol-indophenol by reduced nicotinamide adenine dinucleotide (NADH(2)) have been separated from sonic extracts of Aerobacter aerogenes B199 by diethylaminoethyl (DEAE) cellulose chromatography. Three major chromatographic fractions (enzymes I, II, and III) account for most of the activity in the extract. Of the two minor fractions, one is associated with cytochrome b(1). The other is extremely labile, and was not studied further. The chromatographed diaphorases appear to have a specific requirement for flavin mononucleotide. They are also readily inactivated by dilution; however, this can be prevented by a combination of phosphate buffer, bovine serum albumin, and flavin mononucleotide. The different enzymes are clearly distinguishable by their activities with NADH(2) and reduced nicotinamide adenine dinucleotide phosphate (NADPH(2)) in the presence of various electron acceptors (2,6-dichlorophenol-indophenol, ferricyanide, menadione, and cytochrome c), and by their responses to inhibitors (amobarbital, antimycin A, Atabrine, p-chloromercuribenzenesulfonate, dicumarol, and 2,4-dinitrophenol). With 2,6-dichlorophenol-indophenol as acceptor, enzymes I, II, and III have comparable activities with either NADH(2) or NADPH(2). With menadione and ferricyanide as acceptors, enzymes II and III exhibit very high, NADH(2)-specific activities. When cytochrome c is the acceptor, however, enzyme III shows greater activity with NADPH(2) as the electron donor. Ferricyanide is the most active acceptor for the cytochrome b(1)-containing fraction. Coenzyme Q(6) does not appear to serve as an acceptor. All the diaphorases, with the exception of that in the cytochrome b(1)-containing fraction, are inhibited by p-chloromercuribenzenesulfonate. Amobarbital is relatively ineffective and inhibits only the indophenol reductase activity of enzyme I. The menadione reductase activity of enzymes I, and II, and the diaphorases in the cytochrome b(1)-containing fraction are strongly inhibited by antimycin A, 2,4-dinitrophenol, dicumarol, and Atabrine. However, the menadione reductase activity of enzyme III is affected only by the last three of these inhibitors. The diaphorases in sonic-treated extracts do not appear to be associated with a particulate fraction.

Antimetabolites↗