Garwin J L, Klages A L, Cronan J E
J Biol Chem. 1980 Dec 25;255(24):11949-56.
Beta-Ketoacyl-acyl carrier protein synthases I and II of Escherichia coli were purified and characterized. Synthase I was shown to have a molecular weight of 80,000 +/- 5,000 and to be composed of two similarly sized subunits. Synthase II had a molecular weight of 85,000 +/- 5,000 and also was apparently homodimeric. Gel electrophoresis of partial proteolytic digests demonstrated that synthases I and II share few if any common peptides. Synthases I and II also were shown to be unrelated by immunological criteria. An improved assay for beta-ketoacyl-acyl carrier protein synthase activity gave kinetic parameters for synthases I and II at both 27 degrees C and 37 degrees C using five long chain acyl-acyl carrier protein substrates. The properties of synthase II are consistent with the proposed role of this enzyme in the modulation of fatty acid synthesis by temperature. fabF mutants of E. coli lack synthase II. The fabF locus was mapped at min 24.5 of the E. coli genetic map and the clockwise map order was found to be pyrC, fabD, fabF, purB.
对大肠杆菌的β-酮脂酰-酰基载体蛋白合酶I和II进行了纯化和特性分析。合酶I的分子量为80,000±5,000，由两个大小相似的亚基组成。合酶II的分子量为85,000±5,000，显然也是同型二聚体。部分蛋白酶解消化产物的凝胶电泳表明，合酶I和II几乎没有共同的肽段。从免疫学标准来看，合酶I和II也没有关联。一种改进的β-酮脂酰-酰基载体蛋白合酶活性测定方法，使用五种长链酰基-酰基载体蛋白底物，给出了合酶I和II在27℃和37℃时的动力学参数。合酶II的特性与该酶在温度调节脂肪酸合成中所起的作用一致。大肠杆菌的fabF突变体缺乏合酶II。fabF基因座定位于大肠杆菌遗传图谱的24.5分钟处，顺时针图谱顺序为pyrC、fabD、fabF、purB。
