scholarly journals Effects of glucose on the cytosolic ration of reduced/oxidized nicotinamide-adenine dinucleotide phosphate in rat islets of Langerhans

1979 ◽  
Vol 184 (3) ◽  
pp. 697-700 ◽  
Author(s):  
S J H Ashcroft ◽  
M R Christie
Keyword(s):  
Islets Of Langerhans ◽  
Nicotinamide Adenine Dinucleotide ◽  
Malic Enzyme ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Rat Islets ◽  
Equilibrium Reaction ◽  
Rat Islets Of Langerhans

The maximal extractable activity of “malic” enzyme (EC 1.1.1.40) in rat islets of Langerhans was similar to that reported for liver. Thus “malic” enzyme may catalyse a near-equilibrium reaction in the cytosol of islets of Langerhans. Measurements of islet content of malate and pyruvate, the metabolite substrate and product of “malic” enzyme, were therefore used to calculate the cytosolic ration of [NADPH]/[NADP+]. This ratio was higher in islets incubated with 20 mM-glucose than in islets incubated with 2 mM-glucose.

scholarly journals Interactions of nicotinamide-adenine dinucleotide phosphate analogues and fragments with pigeon liver malic enzyme. Synergistic effect between the nicotinamide and adenine moieties

1987 ◽  
Vol 245 (2) ◽  
pp. 407-414 ◽  
Author(s):  
H J Lee ◽  
G G Chang
Keyword(s):  
Synergistic Effect ◽  
Nicotinamide Adenine Dinucleotide ◽  
Malic Enzyme ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nucleotide Binding ◽  
Phosphate Group ◽  
Nicotinamide Adenine ◽  
Oxidative Decarboxylation ◽  
Wide Range ◽  
Pigeon Liver

The structural requirements of the NADP+ molecule as a coenzyme in the oxidative decarboxylation reaction catalysed by pigeon liver malic enzyme were studied by kinetic and fluorimetric analyses with various NADP+ analogues and fragments. The substrate L-malate had little effect on the nucleotide binding. Etheno-NADP+, 3-acetylpyridine-adenine dinucleotide phosphate, and nicotinamide-hypoxanthine dinucleotide phosphate act as alternative coenzymes for the enzyme. Their kinetic parameters were similar to that of NADP+. Thionicotinamide-adenine dinucleotide phosphate, 3-aminopyridine-adenine dinucleotide phosphate, 5′-adenylyl imidodiphosphate, nicotinamide-adenine dinucleotide 3′-phosphate and NAD+ act as inhibitors for the enzyme. The first two were competitive with respect to NADP+ and non-competitive with respect to L-malate; the other inhibitors were non-competitive with NADP+. All NADP+ fragments were inhibitory to the enzyme, with a wide range of affinity, depending on the presence or absence of a 2′-phosphate group. Compounds with this group bind to the enzyme 2-3 orders of magnitude more tightly than those without this group. Only compounds with this group were competitive inhibitors with respect to NADP+. We conclude that the 2′-phosphate group is crucial for the nucleotide binding of this enzyme, whereas the carboxyamide carbonyl group of the nicotinamide moiety is important for the coenzyme activity. There is a strong synergistic effect between the binding of the nicotinamide and adenosine moieties of the nucleotide molecule.

Effect of Niacin on Mitochondria of Allium Cepa Root Cells

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.

Opioid peptides in rat islets of Langerhans. Immunoreactive met- and leu-enkephalins and BAM-22P

Diabetes ◽  
1986 ◽  
Vol 35 (1) ◽  
pp. 52-57 ◽  
Author(s):  
K. I. Timmers ◽  
N. R. Voyles ◽  
C. King ◽  
M. Wells ◽  
R. Fairtile ◽  
...  
Keyword(s):  
Islets Of Langerhans ◽  
Opioid Peptides ◽  
Rat Islets ◽  
Rat Islets Of Langerhans

Effects of epicatechin on rat islets of Langerhans

Diabetes ◽  
1984 ◽  
Vol 33 (3) ◽  
pp. 291-296 ◽  
Author(s):  
C. S. Hii ◽  
S. L. Howell
Keyword(s):  
Islets Of Langerhans ◽  
Rat Islets ◽  
Rat Islets Of Langerhans
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