scholarly journals Biosynthesis of acetyl-coenzyme A in the electric organ of Torpedo marmorata in relation to acetylcholine metabolism

1977 ◽  
Vol 166 (3) ◽  
pp. 447-453 ◽  
Author(s):  
M F Diebler ◽  
Y Morot-Gaudry
Keyword(s):  
Choline Acetyltransferase ◽  
Gel Filtration ◽  
Electric Organ ◽  
Nerve Endings ◽  
Tissue Extract ◽  
Torpedo Marmorata ◽  
Forward Reaction ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Acetylcholine Metabolism

Formation of acetyl-CoA through acetyl-CoA synthetase (forward reaction) and through choline acyltransferase (backward reaction) was investigated in tissue extract from the electric organ of Torpedo marmorata. When the tissue extract was submitted to gel filtration on Sephadex G-25, the formation of acetyl-CoA by acetyl-CoA synthetase appeared fully dependent on ATP and CoA and partially dependent on acetate (an endogenous supply of acetate is discussed). Choline acetyltransferase was a potent source of acetyl-CoA, only requiring acetylcholine and CoA, and was much more efficient than acetyl-CoA synthetase for concentrations of acetylcholine likely to be present in nerve endings.

scholarly journals THE FINE STRUCTURE OF THE ELECTRIC ORGAN OF TORPEDO MARMORATA

1965 ◽  
Vol 24 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Michael N. Sheridan
Keyword(s):  
Fine Structure ◽  
Connective Tissue ◽  
Basement Membrane ◽  
Intercellular Space ◽  
Electric Organ ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Nerve Fibers ◽  
Nerve Endings ◽  
Torpedo Marmorata

The fine structure of the electric organ of the fish Torpedo marmorata has been examined after osmium tetroxide or potassium permanganate fixation, acetone dehydration, and Araldite embedment. This organ consists of stacks of electroplaques which possess a dorsal noninnervated and a ventral richly innervated surface. Both surfaces are covered with a thin basement membrane. A tubular membranous network whose lumen is continuous with the extracellular space occupies the dorsal third of the electroplaque. Nerve endings, separated from the ventral surface of the electroplaque by a thin basement membrane, contain synaptic vesicles (diameter 300 to 1200 A), mitochondria, and electron-opaque granules (diameter 300 A). Projections from the nerve endings occupy the lumina of the finger-like invaginations of the ventral surface. The cytoplasm of the electroplaques contains the usual organelles. A "cellular cuff" surrounds most of the nerve fibers in the intercellular space, and is separated from the nerve fibre and its Schwann cell by a space containing connective tissue fibrils. The connective tissue fibrils and fibroblasts in the intercellular space are primarily associated with the dorsal surface of the electroplaque.

scholarly journals Subcellular localization and ionic properties of acetyl-coenzyme A synthetase in the electric organ of Torpedo marmorata

1979 ◽  
Vol 180 (2) ◽  
pp. 297-301 ◽  
Author(s):  
Y Morot-Gaudry ◽  
M F Diebler
Keyword(s):  
Enzyme Activity ◽  
Soluble Fraction ◽  
Electric Organ ◽  
Substantial Part ◽  
Synthetase Activity ◽  
Mitochondrial Enzyme ◽  
Torpedo Marmorata ◽  
Acetyl Coenzyme A ◽  
Optimal Activity ◽  
Maximal Activation

Acetyl-CoA synthetase activity was shown to be present in pure cholinergic synaptosomes from electric organ of Torpedo marmorata. After osmotic disruption of synaptosomes a substantial part of the activity was recovered in the soluble fraction. The effects of varying pH and increasing K+ concentrations on the synaptosomal enzyme activity were shown to differ from those observed with the mitochondrial enzyme. Whereas this latter enzyme showed optimal activity above pH 8.5, and a maximal activation in the presence of 120 mM-K+, the synaptosomal enzyme exhibited an optimal activity at pH 7.9 and a moderate K+ stimulatory effect with an optimal concentration of 30 mM.

scholarly journals Deacylation of acetyl-coenzyme A and acetylcarnitine by liver preparations

1978 ◽  
Vol 171 (2) ◽  
pp. 299-303 ◽  
Author(s):  
A M Snoswell ◽  
P K Tubbs
Keyword(s):  
Gel Filtration ◽  
Mitochondrial Fraction ◽  
Liver Mitochondria ◽  
Carnitine Acetyltransferase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Sheep Liver ◽  
Chain Acyl ◽  
Coa Hydrolase ◽  
Hydrolysis Of

The breakdown of acetylcarnitine catalysed by extracts of rat and sheep liver was completely abolished by Sephadex G-25 gel filtration, whereas the hydrolysis of acetyl-CoA was unaffected. Acetyl-CoA and CoA acted catalytically in restoring the ability of Sephadex-treated extracts to break down acetylcarnitine, which was therefore not due to an acetylcarnitine hydrolase but to the sequential action of carnitine acetyltransferase and acetyl-CoA hydrolase. Some 75% of the acetyl-CoA hydrolase activity of sheep liver was localized in the mitochondrial fraction. Two distinct acetyl-CoA hydrolases were partially purified from extracts of sheep liver mitochondria. Both enzymes hydrolysed other short-chain acyl-CoA compounds and succinyl-CoA (3-carboxypropionyl-CoA), but with one acetyl-CoA was the preferred substrate.

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