Kiechle F L, Staudacher D M, Ofenstein J P
Department of Clinical Pathology, William Beaumont Hospital, Royal Oak, MI 48073-6769.
Ann Clin Lab Sci. 1994 Sep-Oct;24(5):422-30.
Tyrphostins inhibit tyrosine kinases and have little effect on the activity of serine/threonine kinases. Pyruvate dehydrogenase kinase inactivates pyruvate dehydrogenase by phosphorylating serine residues within the multienzyme complex. This serine/theronine kinase represents a new family of protein kinases, and one (tyrphostin 47) of two tyrphostins tested appeared to activate the pyruvate dehydrogenase kinase as determined by [1-14C]-lactate oxidation to 14CO2. Experiments designed to determine if the tyrphostins altered pyruvate dehydrogenase activity in mitochondria prepared from rat epididymal adipocytes using [1-14C]-pyruvate as the substrate demonstrated a dose dependent increase in enzyme activity in the presence of tyrphostin 47, but not in tyrphostin 23. This apparent stimulation of pyruvate dehydrogenase activity was attributed to tyrphostin 47's ability to nonenzymatically decarboxylate [1-14C]-pyruvate, the substrate for the pyruvate dehydrogenase assay. Neither tyrphostin directly altered pyruvate dehydrogenase kinase activity. Therefore, assays utilizing [1-14C]-pyruvate and tyrphostin 47 are subject to analytical interference.
tyrphostins抑制酪氨酸激酶，对丝氨酸/苏氨酸激酶的活性影响很小。丙酮酸脱氢酶激酶通过磷酸化多酶复合物中的丝氨酸残基使丙酮酸脱氢酶失活。这种丝氨酸/苏氨酸激酶代表了一个新的蛋白激酶家族，在所测试的两种tyrphostins中，有一种（tyrphostin 47）似乎能激活丙酮酸脱氢酶激酶，这是通过[1-14C]-乳酸氧化为14CO2来确定的。旨在确定tyrphostins是否改变以[1-14C]-丙酮酸为底物从大鼠附睾脂肪细胞制备的线粒体中丙酮酸脱氢酶活性的实验表明，在tyrphostin 47存在下，酶活性呈剂量依赖性增加，而在tyrphostin 23存在下则没有。丙酮酸脱氢酶活性的这种明显刺激归因于tyrphostin 47非酶促脱羧[1-14C]-丙酮酸的能力，[1-14C]-丙酮酸是丙酮酸脱氢酶测定的底物。两种tyrphostin都没有直接改变丙酮酸脱氢酶激酶的活性。因此，利用[1-14C]-丙酮酸和tyrphostin 47的测定受到分析干扰。
