scholarly journals Measurement of the rates of acetyl-CoA hydrolysis and synthesis from acetate in rat hepatocytes and the role of these fluxes in substrate cycling

1990 ◽  
Vol 270 (1) ◽  
pp. 219-225 ◽  
Author(s):  
B Crabtree ◽  
M J Gordon ◽  
S L Christie
Keyword(s):  
Heat Production ◽  
Rat Hepatocytes ◽  
Total Heat ◽  
Acetate Production ◽  
Acetyl Coa ◽  
Acetyl Coa Synthesis ◽  
Acetate Utilization ◽  
Net Flux

1. Acetyl-CoA hydrolysis, acetyl-CoA synthesis from acetate and several related fluxes were measured in rat hepatocytes. 2. In contrast with acetyl-CoA hydrolysis, most of the acetyl-CoA synthesis from acetate occurred in the mitochondria. 3. Acetyl-CoA hydrolysis was not significantly affected by 24 h starvation or (-)-hydroxycitrate. 4. In the cytoplasm there was a net flux of acetyl-CoA to acetate, and substrate cycling between acetate and acetyl-CoA in this compartment was very low, accounting for less than 0.1% of the total heat production by the animal. 5. A larger cycle, involving mitochondrial and cytoplasmic acetate and acetyl-CoA, may operate in fed animals, but would account for only approx 1% of total heat production. 6. It is proposed that the opposing fluxes of mitochondrial acetate utilization and cytoplasmic net acetate production may provide sensitivity, feedback and buffering, even when these fluxes are not linked to form a conventional substrate cycle.

Species-Specific Differences in Acetyl Coenzyme A Synthesis of Chloroplasts

1986 ◽  
Vol 41 (7-8) ◽  
pp. 733-740 ◽  
Author(s):  
Hans-Jürgen Treede ◽  
Burgi Riens ◽  
Klaus-Peter Heise
Keyword(s):  
Fatty Acid ◽  
Acid Synthesis ◽  
Kinetic Properties ◽  
Acetyl Coa ◽  
Acetyl Coa Synthesis ◽  
Different Types ◽  
Leaf Tissues ◽  
Species Specific ◽  
Control Criteria

Abstract Acetyl-CoA and Fatty Acid Synthesis, Chloroplasts The present investigation indicates that photosynthetically active chloroplasts can synthesize acetyl-CoA either from acetate via acetyl-CoA synthetase (ACS) or from pyruvate via the pyru­ vate dehydrogenase complex (PDC). Both enzyme systems have been assayed in rapidly prepared extracts of chloroplasts isolated from spinach, peas and maize mesophyll. Their kinetic properties showed few species-specific differences. The differing pyruvate and acetate concentrations within the corresponding leaf tissues have been interpreted, therefore, as constituting a major factor determining the relative involvement of both acetyl-CoA synthesizing systems within the different types of chloroplasts. The idea that acetate originates from mitochondria and pyruvate from the cytosol has been supported by nonaqueous fractionation studies. Diffusion-mediated faster up­ take of acetate may indicate a predominant role of the ACS in spinach chloroplasts. Higher cellular pyruvate/acetate-ratios (2-5) in pea and maize leaves may enhance pyruvate uptake into chloroplasts and thus PDC-driven acetyl-CoA synthesis in pea and maize mesophyll chloroplasts. Maize mesophyll chloroplasts even show a light-driven pyruvate uptake accompanied by a stimulated acetyl-CoA and fatty acid formation. Assuming light-dependent increasing parameters in the stroma space, like Mg2+-concentrations, pH and ATP, as further control criteria in chloroplast acetyl-CoA formation, the ACS appears better adapted to the circumstances in illuminated chloroplasts because of the fact that 1. the ACS requires these cofactors altogether; 2. the PDC is stimulated by increasing pH (up to 8) and Mg-levels (up to 5 mᴍ) alone.

scholarly journals Inhibition of ureagenesis by valproate in rat hepatocytes. Role of N-acetylglutamate and acetyl-CoA

1983 ◽  
Vol 216 (1) ◽  
pp. 233-236 ◽  
Author(s):  
F X Coude ◽  
G Grimber ◽  
P Parvy ◽  
D Rabier ◽  
F Petit
Keyword(s):  
Rat Hepatocytes ◽  
Urea Synthesis ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Acetyl Coa ◽  
Isolated Rat Hepatocytes ◽  
Cellular Concentration ◽  
Acetylglutamate Synthase ◽  
Ornithine Transcarbamoylase

Valproate (0.5-5 mM) strongly inhibited urea synthesis in isolated rat hepatocytes incubated with 10 mM-alanine and 3 mM-ornithine. Valproate at the same concentrations markedly decreased concentrations of N-acetylglutamate, an essential activator of carbamoyl-phosphate synthetase I (EC 6.3.4.16), in parallel with the inhibition of urea synthesis by valproate. This compound also lowered the cellular concentration of acetyl-CoA, a substrate of N-acetylglutamate synthase (EC 2.3.1.1); glutamate, aspartate and citrulline were similarly decreased. Valproate in a dose up to 2 mM did not significantly affect the cellular concentration of ATP and had no direct effect on N-acetylglutamate synthesis, carbamoyl-phosphate synthetase I and ornithine transcarbamoylase (EC 2.1.3.3) activities.

The role of rice bran extract on acetyl CoA carboxylase in liver of rats fed a high-fat diet

Planta Medica ◽  
2011 ◽  
Vol 77 (12) ◽  
Author(s):  
C Charkhonpunya ◽  
S Sireeratawong ◽  
S Komindr ◽  
N Lerdvuthisopon
Keyword(s):  
Rice Bran ◽  
High Fat Diet ◽  
Acetyl Coa Carboxylase ◽  
High Fat ◽  
Acetyl Coa ◽  
Rice Bran Extract
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