Crotonyl Coenzyme A Reductase Activity of Bovine Mammary Fatty Acid Synthetase

Lactating bovine mammary fatty acid synthetase, the enzyme complex that synthesizes fatty acids from a primer, malonyl-CoA, and TPNH, is shown to have a relatively high crotonyl-CoA reductase activity. Throughout purification to homogeneity the ratio of the reductase to the synthetase activities rem...

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Bibliographic Details
Published in:The Journal of biological chemistry 1974-01, Vol.249 (1), p.111-117
Main Authors: Maitra, Shyamal K., Kumar, Soma
Format: Article
Language:English
Subjects:
Acetyl Coenzyme A
Aluminum
Animals
Butyrates
Carbon Radioisotopes
Cattle
Chromatography
Chromatography, DEAE-Cellulose
Chromatography, Gel
Coenzyme A
Crotonates
Dithiothreitol - pharmacology
Fatty Acid Synthases - isolation & purification
Female
Hydrogen-Ion Concentration
Kinetics
Lactation
Mammary Glands, Animal - enzymology
Mercaptoethanol
NADP
Oxidoreductases - isolation & purification
Oxidoreductases - metabolism
Pregnancy
Protein Binding
Temperature
Time Factors
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Summary:Lactating bovine mammary fatty acid synthetase, the enzyme complex that synthesizes fatty acids from a primer, malonyl-CoA, and TPNH, is shown to have a relatively high crotonyl-CoA reductase activity. Throughout purification to homogeneity the ratio of the reductase to the synthetase activities remains constant and the two activities emerge superimposed on gel filtration. Although the investigation showed that the reductase activity of the enzyme is an inherent property of the enzyme, the pH profiles and the rates of recovery of the two activities of the enzyme by preincubation were not the same. Synthetase gave a bell-shaped pH profile with an optimum at pH 6.8 while the reductase reaction showed maximum activity in the range of pH 7 to 8.5. The reductase activity was influenced by preincubation while the synthetase was not. The crotonyl-CoA reductase reaction requires TPNH as electron donor, but at a 20-fold higher concentration DPNH will substitute for TPNH with 50% Vmax. As a result of the presence of the reductase activity crotonyl-CoA substitutes as a primer in fatty acid synthesis as effectively as butyryl-CoA, a primer decidedly better than acetyl-CoA.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(19)43098-6