Stimulation of the Transhydrogenase Activity of Spinach Ferredoxin-Nicotinamide Adenine Dinucleotide Phosphate Reductase by Ferredoxin

Combination of preincubated drug-metabolizing medium containing NADP+ with a cell-free protein-synthesizing system resulted in marked stimulation of incorporation of L-[1-14C]leucine into protein. Addition of 4-dimethylamino-3′-methylazobenzene, present and previously preincubated in the drug-metabolizing medium, decreased this effect.

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The isocitrate dehydrogenases of Acinetobacter lwoffi. Studies on the regulation of nicotinamide–adenine dinucleotide phosphate-linked isoenzyme

Biochemical Journal ◽

10.1042/bj1320215 ◽

1973 ◽

Vol 132 (2) ◽

pp. 215-221 ◽

Cited By ~ 15

Author(s):

Colin H. Self ◽

Malcolm G. Parker ◽

P. David J. Weitzman

Keyword(s):

Molecular Weight ◽

Nicotinamide Adenine Dinucleotide ◽

Nicotinamide Adenine Dinucleotide Phosphate ◽

Nicotinamide Adenine ◽

Ph Optimum ◽

Low Concentrations ◽

Molecular Weight Form ◽

Metabolic Significance ◽

Regulatory Sites ◽

Stimulation Of

Of the two NADP-linked isocitrate dehydrogenases in Acinetobacter lwoffi the higher-molecular-weight form, isoenzyme-II, is reversibly stimulated sixfold by low concentrations of glyoxylate or pyruvate. Kinetic results indicate that this stimulation of activity involves both an increase in Vmax. and a decrease in the apparent Km values for substrates, most markedly that for NADP+. Other changes brought about by glyoxylate or pyruvate include a shift in the pH optimum for activity and an increased stability to inactivation by heat or urea. Mixtures of glyoxylate plus oxaloacetate, known to inhibit isocitrate dehydrogenases from other organisms, produce inhibition of both A. lowffi isoenzymes, and do not reflect the stimulatory specificity of glyoxylate for isoenzyme-II. Isoenzyme-II is also stimulated by AMP and ADP, but the activation by glyoxylate or pyruvate is shown to be quite independent of the adenylate activation. Differential desensitization of the enzyme by urea to the two types of activator further supports the view that the enzyme possesses two distinct allosteric regulatory sites. The metabolic significance of the activations is discussed.

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EFFECTS OF LUTEINIZING HORMONE AND NICOTINAMIDE ADENINE DINUCLEOTIDE PHOSPHATE ON SYNTHESIS OF PROGESTATIONAL STEROIDS BY RABBIT OVARIAN TISSUE IN VITRO

Journal of Endocrinology ◽

10.1677/joe.0.0350065 ◽

1966 ◽

Vol 35 (1) ◽

pp. 65-73 ◽

Cited By ~ 3

Author(s):

J. H. DORRINGTON ◽

R. KILPATRICK

Keyword(s):

Luteinizing Hormone ◽

Nicotinamide Adenine Dinucleotide ◽

Ovarian Tissue ◽

Nicotinamide Adenine Dinucleotide Phosphate ◽

Nicotinamide Adenine ◽

Steroid Synthesis ◽

Activity Measurements ◽

Progesterone Synthesis ◽

Stimulation Of

SUMMARY Luteinizing hormone (LH) stimulated synthesis of both progesterone and 20α-hydroxypregn-4-en-3-one by rabbit ovarian tissue in vitro. Progesterone synthesis was stimulated by nicotinamide adenine dinucleotide phosphate (NADP), but 20α-hydroxypregn-4-en-3-one production was only slightly affected by NADP compared with the effect of LH. When NADP was added with glucose-6-phosphate (G-6-P) or 6-phospho-gluconate (6-P-G), no apparent stimulation of progestational steroid synthesis occurred. Specific activity measurements suggested that stimulation of synthesis was masked by increased conversion of progestational steroids to other products. When NADP and submaximal concentrations of LH were used together, potentiation rather than addition of effects on progesterone synthesis was found, and addition of effects with supramaximal concentrations of LH. No potentiation was found when NADP was replaced by NADP and G-6-P or 6-P-G, or by NADPH2. NADP, unlike LH, caused striking stimulation of progesterone synthesis by separated corpora lutea. It is suggested that the present results provide further support for the view that the actions of LH and NADP are related.

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Effect of Niacin on Mitochondria of Allium Cepa Root Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060404 ◽

1967 ◽

Vol 25 ◽

pp. 78-79

Author(s):

M. Arif Hayat

Keyword(s):

Nicotinamide Adenine Dinucleotide ◽

Hydrogen Transfer ◽

Nicotinamide Adenine Dinucleotide Phosphate ◽

Nicotinamide Adenine ◽

Root Tips ◽

Root Cells ◽

Transfer Processes ◽

Standard Procedures ◽

A Cell ◽

Critical Interest

Although it is recognized that niacin (pyridine-3-carboxylic acid), incorporated as the amide in nicotinamide adenine dinucleotide (NAD) or in nicotinamide adenine dinucleotide phosphate (NADP), is a cofactor in hydrogen transfer in numerous enzyme reactions in all organisms studied, virtually no information is available on the effect of this vitamin on a cell at the submicroscopic level. Since mitochondria act as sites for many hydrogen transfer processes, the possible response of mitochondria to niacin treatment is, therefore, of critical interest.Onion bulbs were placed on vials filled with double distilled water in the dark at 25°C. After two days the bulbs and newly developed root system were transferred to vials containing 0.1% niacin. Root tips were collected at ¼, ½, 1, 2, 4, and 8 hr. intervals after treatment. The tissues were fixed in glutaraldehyde-OsO4 as well as in 2% KMnO4 according to standard procedures. In both cases, the tissues were dehydrated in an acetone series and embedded in Reynolds' lead citrate for 3-10 minutes.

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