Nishino T, Murao S, Wada H
J Biochem. 1984 May;95(5):1283-8. doi: 10.1093/oxfordjournals.jbchem.a134733.
The inactivation mechanism of pyridoxal phosphate-linked mitochondrial aspartate transaminase (pig heart) by gostatin (5-amino-2-carboxy-4-oxo-1,4,5,6-tetrahydropyridine-3-acetic acid), a novel amino acid produced by Streptomyces sumanensis, was investigated. Gostatin is a time-dependent inhibitor of the enzyme giving an enzyme half-life of 1.8 min at 3.1 microM (25 degrees C). The kinetic properties of the inhibitor suggest that it is a suicide substrate (mechanism-based inhibitor) of the enzyme, and the observed Ki is 59 microM and Kcat is 0.11S-1 at 25 degrees C. Incubation of the enzyme with a stoichiometric amount of the inhibitor (1 mol of inhibitor/1 mol of enzyme monomer) results in complete inactivation. Spectrophotometric titration and gel filtration experiments indicate the binding of 1 mol of gostatin with 1 mol of enzyme monomer. Gostatin serves as an efficient titrant for the enzyme. Liberation of a compound having inhibitory activity against the apo-form enzyme from the enzyme-inhibitor complex under denaturing conditions suggests irreversible modification of the cofactor.
研究了由苏门答腊链霉菌产生的一种新型氨基酸戈他汀（5-氨基-2-羧基-4-氧代-1,4,5,6-四氢吡啶-3-乙酸）对磷酸吡哆醛连接的线粒体天冬氨酸转氨酶（猪心）的失活机制。戈他汀是该酶的时间依赖性抑制剂，在3.1微摩尔（25℃）时酶的半衰期为1.8分钟。抑制剂的动力学性质表明它是该酶的自杀底物（基于机制的抑制剂），在25℃下观察到的Ki为59微摩尔，Kcat为0.11秒⁻¹。将酶与化学计量的抑制剂（1摩尔抑制剂/1摩尔酶单体）一起孵育会导致完全失活。分光光度滴定和凝胶过滤实验表明1摩尔戈他汀与1摩尔酶单体结合。戈他汀可作为该酶的有效滴定剂。在变性条件下从酶-抑制剂复合物中释放出对脱辅基形式酶具有抑制活性的化合物，这表明辅因子发生了不可逆修饰。
