scholarly journals Biosynthesis of fatty acids in cell-free preparations. 2. Synthesis of fatty acids from acetate by a soluble enzyme system prepared from rat mammary gland

1955 ◽  
Vol 60 (1) ◽  
pp. 147-155 ◽  
Author(s):  
G. Popják ◽  
Alisa Tietz
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Enzyme System ◽  
Soluble Enzyme ◽  
Rat Mammary Gland

scholarly journals Rat mammary-gland acetyl-coenzyme A carboxylase. Interaction with milk fatty acids

1970 ◽  
Vol 118 (4) ◽  
pp. 645-657 ◽  
Author(s):  
A. L. Miller ◽  
Mary E. Geroch ◽  
H. Richard Levy
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Complex Mixture ◽  
Acid Synthesis ◽  
Acetyl Coa Carboxylase ◽  
High Concentration ◽  
Acetyl Coa ◽  
Milk Fatty Acids ◽  
Low Concentrations ◽  
Rat Mammary Gland

1. Highly purified rat mammary-gland acetyl-CoA carboxylase was inhibited by milk obtained from rats 12h after their young were weaned. 2. All the inhibitory activity was found in the particulate fraction (R105) obtained on centrifuging the milk. It could be extracted from milk fraction R105 with acetone and identified as a complex mixture of non-esterified fatty acids, present in high concentration (nearly 10mm) in the milk. 3. Inhibition of acetyl-CoA carboxylase was observed at low concentrations (0.2–20μm) of several of these fatty acids when fresh fully active enzyme was used. Enzyme that had been partly inactivated by aging, or by storing in the absence of citrate, was stimulated by low concentrations but inhibited by high concentrations of fatty acids. 4. Various experiments suggested that fatty acids produce irreversible inactivation of acetyl-CoA carboxylase. 5. The effects of palmitoyl-CoA on mammary-gland acetyl-CoA carboxylase were found to resemble those of fatty acids, except that palmitoyl-CoA was effective at lower concentration. 6. The effect of milk fraction R105 was tested on six other enzymes previously shown to decline to various extents after weaning. Although several of these enzymes were affected by unfractionated milk fraction R105, none was significantly inhibited by the acetone extract or by low concentrations of lauric acid. 7. The findings are consistent, both qualitatively and quantitatively, with a regulatory mechanism whereby milk fatty acids shut off fatty acid synthesis in the mammary gland after weaning by inhibiting acetyl-CoA carboxylase.

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