Mackall J C, Lane M D
Biochem J. 1977 Mar 15;162(3):635-42. doi: 10.1042/bj1620635.
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.
研究了泌乳开始后大鼠乳腺组织中乙酰辅酶A羧化酶活性升高的过程。在泌乳分化过程中，测定了酶活性的变化动力学以及用抗禽肝乙酰辅酶A羧化酶抗体进行免疫滴定的酶量。该抗体可使大鼠乳腺组织以及鸡肝细胞溶胶中的乙酰辅酶A羧化酶失活并特异性沉淀。通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳对乳腺组织羧化酶的免疫沉淀物进行表征，发现一条约230000分子量的含生物素的单一多肽。该分子量约为报道的禽肝酶分子量的两倍。然而，在存在胰蛋白酶抑制剂的情况下制备并进行免疫沉淀的鸡肝细胞溶胶，通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳测定，产生了一个230000分子量的含生物素亚基；省略蛋白酶抑制剂会导致一个约为该大小一半的亚基。在整个妊娠期，羧化酶活性和可免疫滴定的酶量均保持在低水平；然而，分娩后这两个参数同时上升至初始值的30 - 40倍。因此，乙酰辅酶A羧化酶浓度的升高似乎是由于酶的合成速率相对于降解速率增加，而不是由于预先存在的酶形式被激活。
