Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
FEBS Lett. 2012 Apr 5;586(7):1049-54. doi: 10.1016/j.febslet.2012.02.054. Epub 2012 Mar 9.
Phosphoenolpyruvate carboxylase (PEPC) is a tightly controlled anaplerotic enzyme situated at a pivotal branch point of plant carbohydrate-metabolism. In developing castor oil seeds (COS) a novel allosterically-densensitized 910-kDa Class-2 PEPC hetero-octameric complex arises from a tight interaction between 107-kDa plant-type PEPC and 118-kDa bacterial-type PEPC (BTPC) subunits. Mass spectrometry and immunoblotting with anti-phosphoSer451 specific antibodies established that COS BTPC is in vivo phosphorylated at Ser451, a highly conserved target residue that occurs within an intrinsically disordered region. This phosphorylation was enhanced during COS development or in response to depodding. Kinetic characterization of a phosphomimetic (S451D) mutant indicated that Ser451 phosphorylation inhibits the catalytic activity of BTPC subunits within the Class-2 PEPC complex.
磷酸烯醇式丙酮酸羧化酶（PEPC）是一种受严格调控的生糖氨基酸酶，位于植物碳水化合物代谢的关键分支点。在发育中的蓖麻籽油种子（COS）中，一种新型的变构敏化的 910kDa 类 2PEPC 异源八聚体复合物由 107kDa 植物型 PEPC 和 118kDa 细菌型 PEPC（BTPC）亚基之间的紧密相互作用产生。质谱分析和用抗磷酸丝氨酸 451 特异性抗体的免疫印迹实验表明，COS BTPC 在体内的丝氨酸 451 处发生磷酸化，该位点是一个高度保守的靶位，位于一个无序的区域内。这种磷酸化在 COS 发育过程中或在脱荚过程中增强。磷酸模拟（S451D）突变体的动力学特征表明，BTPC 亚基在类 2PEPC 复合物内的 Ser451 磷酸化抑制其催化活性。
