scholarly journals Medium-chain fatty acid synthesis by goat mammary-gland fatty acid synthetase. The effect of limited proteolysis

1983 ◽  
Vol 209 (1) ◽  
pp. 215-222 ◽  
Author(s):  
I Grunnet ◽  
J Knudsen
Keyword(s):  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Proteolytic Enzymes ◽  
Limited Proteolysis ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Medium Chain ◽  
The Core ◽  
Chain Acyl

Fatty acid synthetase from goat mammary gland was subjected to limited proteolysis by trypsin and elastase. Both proteolytic enzymes selectively cleaved the chain-terminating thioester hydrolase component from the enzyme complex, leaving all other partial activities intact in the core peptides. Trypsin, but not elastase, caused extensive degradation of the released thioester hydrolase. The released thioester hydrolase could be purified to homogeneity by gel filtration. The molecular weight was estimated as 29 000 and the enzyme showed only significant hydrolytic activity toward long-chain acyl-CoA esters. The core peptides retained the ability to synthesize medium-chain acyl-CoA esters in the presence of 2,6-di-O-methyl-alpha-cyclodextrin. The results conclusively show that the terminating thioester hydrolase of goat mammary-gland fatty acid synthetase is not involved in termination of medium-chain-length fatty acid synthesis by this enzyme.

scholarly journals Purification and some properties of a medium-chain acyl-thioester hydrolase from lactating-rabbit mammary gland which terminates chain elongation in fatty acid synthesis

1976 ◽  
Vol 160 (3) ◽  
pp. 683-691 ◽  
Author(s):  
J Knudsen ◽  
S Clark ◽  
R Dils
Keyword(s):  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Chain Elongation ◽  
Medium Chain ◽  
Chain Acyl

1. An acyl-thioester hydrolase was isolated from the cytosol of lactating-rabbit mammary gland. The purified enzyme terminates fatty acid synthesis at medium-chain (C8:0-C12:0) acids when it is incubated with fatty acid synthetase and rate-limiting concentrations of malonyl-CoA. These acids are characteristic products of the lactating gland. 2. The mol.wt. of the enzyme is 29000±500 (mean±S.D. of three independent preparations), as estimated by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. 3. The enzyme also hydrolyses acyl-CoA esters of chain lengths C10:0-C16:0 when these are used as model substrates. The greatest activity was towards dodecanoyl-CoA, and the three preparations had specific activities of 305, 1130 and 2010 nmol of dodecanoyl-CoA hydrolysed/min per mg of protein when 56muM substrate was used. 4. The way in which this enzyme controls the synthesis of medium-chain fatty acids by fatty acid synthetase is briefly discussed.

scholarly journals Medium-chain fatty acid synthesis in lactating-rabbit mammary gland. Intracellular concentration and specificity of medium-chain acyl thioester hydrolase

1979 ◽  
Vol 181 (2) ◽  
pp. 267-274 ◽  
Author(s):  
J Knudsen
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Molar Ratio ◽  
Medium Chain ◽  
Malonyl Coa ◽  
Chain Acyl ◽  
Rate Limiting

The concentration of medium-chain acyl thioester hydrolase and of fatty acid synthetase was determined by rocket immunoelectrophoresis in nine different particle-free supernatant fractions from lactating-rabbit mammary gland. The molar ratio of the hydrolase to fatty acid synthetase was 1.99 +/- 0.66 (mean +/- S.D.). A rate-limiting concentration of malonyl-CoA was required to ensure the predominant synthesis of medium-chain fatty acids when 2 mol of the hydrolase was added per mol of fatty acid synthetase. The interaction of the hydrolase with fatty acid synthetase was concentration-dependent, though an optimum concentration of hydrolase to synthetase could not be obtained. The lactating-rabbit mammary gland hydrolase altered the pattern of fatty acids synthesized by fatty acid synthetases prepared from cow, goat, sheep and rabbit lactating mammary glands, rabbit liver and cow adipose tissue.

scholarly journals A novel acyl-CoA-binding protein from bovine liver. Effect on fatty acid synthesis

1987 ◽  
Vol 241 (1) ◽  
pp. 189-192 ◽  
Author(s):  
I B Mogensen ◽  
H Schulenberg ◽  
H O Hansen ◽  
F Spener ◽  
J Knudsen
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Binding Protein ◽  
Fatty Acid Synthetase ◽  
Bovine Liver ◽  
Acid Synthesis ◽  
Fatty Acid Binding Proteins ◽  
Fatty Acid Binding ◽  
Medium Chain ◽  
Chain Acyl

Bovine liver was shown to contain a hitherto undescribed medium-chain acyl-CoA-binding protein. The protein co-purifies with fatty-acid-binding proteins, but was, unlike these proteins, unable to bind fatty acids. The protein induced synthesis of medium-chain acyl-CoA esters on incubation with goat mammary-gland fatty acid synthetase. The possible function of the protein is discussed.

scholarly journals Transacylation as a chain-termination mechanism in fatty acid synthesis by mammalian fatty acid synthetase. Synthesis of medium-chain-length (C8-C12) acyl-CoA esters by goat mammary-gland fatty acid synthetase

1982 ◽  
Vol 202 (1) ◽  
pp. 139-143 ◽  
Author(s):  
J Knudsen ◽  
I Grunnet
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Medium Chain ◽  
Medium Chain Fatty Acids ◽  
Medium Chain Length ◽  
A Chain ◽  
Chain Fatty Acids

1. Ruminant mammary-gland fatty acid synthetases can, in contrast with non-ruminant mammary enzymes, synthesize medium-chain fatty acids. 2. Medium-chain fatty acids are only synthesized in the presence of a fatty acid-removing system such as albumin, beta-lactoglobulin or methylated cyclodextrin. 3. The short- and medium-chain fatty acids synthesized were released as acyl-CoA esters from the fatty acid synthetase.

scholarly journals Triacylglycerol synthesis in goat mammary gland. The effect of ATP, Mg2+ and glycerol 3-phosphate on the esterification of fatty acids synthesized de novo

1984 ◽  
Vol 220 (2) ◽  
pp. 513-519 ◽  
Author(s):  
H O Hansen ◽  
I Grunnet ◽  
J Knudsen
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Fatty Acid ◽  
De Novo ◽  
Fatty Acid Synthetase ◽  
Acid Synthesis ◽  
Medium Chain ◽  
Medium Chain Fatty Acids ◽  
Triacylglycerol Synthesis ◽  
Chain Fatty Acids

Goat mammary-gland microsomal fraction by itself induces synthesis of medium-chain-length fatty acids by goat mammary fatty acid synthetase and incorporates short- and medium-chain fatty acids into triacylglycerol. Addition of ATP in the absence or presence of Mg2+ totally inhibits triacylglycerol synthesis from short- and medium-chain fatty acids, and severely inhibits synthesis de novo of medium-chain fatty acids. The inhibition by ATP of fatty acid synthesis and triacylglycerol synthesis de novo can be relieved by glycerol 3-phosphate. The effect of ATP could not be mimicked by the non-hydrolysable ATP analogue, adenosine 5′-[beta, gamma-methylene]triphosphate and could not be shown to be caused by inhibition of the diacylglycerol acyltransferase by a phosphorylation reaction. Possible explanations for the mechanism of the inhibition by ATP are discussed, and a hypothetical model for its action is outlined.

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