scholarly journals The activities of nicotinamide-adenine dinucleotide- and nicotinamide-adenine dinucleotide phosphate-linked isocitrate dehydrogenase in insect and vertebrate muscles

1970 ◽  
Vol 116 (4) ◽  
pp. 22P-23P ◽  
Author(s):  
B Crabtree ◽  
E A Newsholme
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine

scholarly journals The role of nicotinamide–adenine dinucleotide phosphate-dependent malate dehydrogenase and isocitrate dehydrogenase in the supply of reduced nicotinamide–adenine dinucleotide phosphate for steroidogenesis in the superovulated rat ovary

1970 ◽  
Vol 117 (1) ◽  
pp. 73-83 ◽  
Author(s):  
A. P. F. Flint ◽  
R. M. Denton
Keyword(s):  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Tissue Homogenate ◽  
Kinetic Properties ◽  
Rat Ovary ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Effect Of Glucose

1. Superovulated rat ovary was found to contain high activities of NADP–malate dehydrogenase and NADP–isocitrate dehydrogenase. The activity of each enzyme was approximately four times that of glucose 6-phosphate dehydrogenase and equalled or exceeded the activities reported to be present in other mammalian tissues. Fractionation of a whole tissue homogenate of superovulated rat ovary indicated that both enzymes were exclusively cytoplasmic. The tissue was also found to contain pyruvate carboxylase (exclusively mitochondrial), NAD–malate dehydrogenase and aspartate aminotransferase (both mitochondrial and cytoplasmic) and ATP–citrate lyase (exclusively cytoplasmic). 2. The kinetic properties of glucose 6-phosphate dehydrogenase, NADP–malate dehydrogenase and NADP–isocitrate dehydrogenase were determined and compared with the whole-tissue concentrations of their substrates and NADPH; NADPH is a competitive inhibitor of all three enzymes. The concentrations of glucose 6-phosphate, malate and isocitrate in incubated tissue slices were raised at least tenfold by the addition of glucose to the incubation medium, from the values below to values above the respective Km values of the dehydrogenases. Glucose doubled the tissue concentration of NADPH. 3. Steroidogenesis from acetate is stimulated by glucose in slices of superovulated rat ovary incubated in vitro. It was found that this stimulatory effect of glucose can be mimicked by malate, isocitrate, lactate and pyruvate. 4. It is concluded that NADP–malate dehydrogenase or NADP–isocitrate dehydrogenase or both may play an important role in the formation of NADPH in the superovulated rat ovary. It is suggested that the stimulatory effect of glucose on steroidogenesis from acetate results from an increased rate of NADPH formation through one or both dehydrogenases, brought about by the increases in the concentrations of malate, isocitrate or both. Possible pathways involving the two enzymes are discussed.

scholarly journals Nicotinamide adenine dinucleotide phosphate-converting enzymes and adenosine triphosphate citrate lyase in some tissues and organs of New Zealand obese mice with special reference to the enzyme pattern of the pancreatic islets.

1975 ◽  
Vol 23 (9) ◽  
pp. 660-665 ◽  
Author(s):  
C Berne
Keyword(s):  
New Zealand ◽  
Pancreatic Islets ◽  
Adenosine Triphosphate ◽  
Isocitrate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
The Other ◽  
Nicotinamide Adenine ◽  
Obese Mice ◽  
Citrate Lyase

In order to obtain a quantitative estimate of the capacity of the pancreatic islets for provision of cytoplasmic acetyl-coenzyme A and for the turnover of nicotinamide adenine dinucleotide phosphate and its reduced form (NADP+/NADPH), the following enzymes were assayed in islets taken from New Zealand Obese mice: adenosine triphosphate citrate lyase (EC 4.1.3.8), malate dehydrogenase (decarboxylating) (NADP+) (EC 1.1.1.40), glutathione reductase (EC 1.6.4.2) and isocitrate dehydrogenase (NADP+) (EC 1.1.1.42). In addition, the activity of isocitrate dehydrogenase (NAD+) (EC 1.1.1.41) was determined. For comparative purposes the activities in exocrine pancreas, liver, heart muscle, kidney cortex and skeletal muscle were also determined. Specimens of pancreatic islets and the other tissues were microdissected from freeze-dried sections. In comparison with the other tissues, adenosine triphosphate citrate lyase was particularly active in the islets. The NADP+/NAPH-converting enzymes had activities, which suggested a rapid turnover of the islet NADP+/NADPH pool.

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