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Purification and some properties of acetyl-coenzyme A carboxylase from rabbit mammary gland.

ABSTRACT: 1. Acetyl-Coa carboxylase from lactating-rabbit mammary gland was purified to homogeneity by the criterion of polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. 2. Use of phosphate buffer throughout the purification gave low recovery of enzyme. Consequently, Tris buffers were used in the extraction and in selected stages of the purification procedure. 3. The purified enzyme had a specific activity of 5.15 +/- 0.3 mumol of bicarbonate incorporated/min per mg of protein (mean +/- S.E.M. of five preparations). This represents a purification of 257 +/- 16-fold and a yield of 4.3 +/- 0.13%. 4. The kinetic parameters of the purified enzyme were similar to those reported for the enzyme from other tissue sources. 5. The enzyme was assayed by a spectrophotometric assay and by a [14C]bicarbonate-fixation assay. Short incubation were used in the radio-chemical assay to avoid substantial loss of [14C]bicarbonate.

SUBMITTER: Manning R

PROVIDER: S-EPMC1172594 | biostudies-other | 1976 Feb

REPOSITORIES: biostudies-other

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Rat mammary-gland acetyl-coenzyme A carboxylase interaction with milk fatty acids.

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Changes in mammary-gland acetyl-coenzyme A carboxylase associated with lactogenic differentiation.

Project description:The process leading to the rise of acetyl-CoA carboxylase activity in rat mammary tissue after the onset of lactation was investigated. The kinetics of change in enzyme activity and enzyme immunotitratable with antibody against avian liver acetyl-CoA carboxylase were determined during the course of lactogenic differentiation. The antibody inactivates and specifically precipitates acetyl-CoA carboxylase from rat mammary tissue as well as that from chicken liver cytosol. Characterization of the immunoprecipitate of the mammary tissue carboxylase by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis reveals a single biotin-containing polypeptide of about 230000mol.wt. This molecular weight is approximately twice that reported for the avian liver enzyme. However, chicken liver cytosol prepared in the presence of trypsin inhibitor and subjected to immunoprecipitation gives rise to a biotin-containing subunit of 230000mol.wt. as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis; omission of proteinase inhibitor leads to a subunit(s) approximately one-half this size. Throughout gestation both carboxylase activity and amounts of immunotitratable enzyme remained low; however, after parturition both parameters rose concomitantly to values 30-40 times the initial values. Therefore the elevated concentration of acetyl-CoA carboxylase appears to result from an increased rate of synthesis of enzyme relative to degradation rather than to activation of a pre-existing form of the enzyme.

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Studies on acetyl-CoA carboxylase and fatty acid synthase from rat mammary gland and mammary tumours.

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