Fazekas S, Berentey G, Györgyi S, Székessy-Hermann V
Second Institute of Biochemistry, Semmelweis University Medical School, Budapest, Hungary.
Acta Physiol Hung. 1987;70(1):133-47.
Earlier the autophosphorylation of myosin and the labile phosphate (P) content of rabbit skeletal muscle was reported [6, 7, 9]. The present paper describes that the endogeneous preformed P level in fresh preparation of exercised muscle is higher than that of untrained control one. It was revealed that the presence of a significant amount of mitochondrial myosin (with much higher P content) in the well-trained human muscle preparations falsified the appreciation of myofibrillar myosin. Therefore, a reliable myofibrillar preparation with correct P content from exercised subjects was obtained only after the separation of mitochondrial fraction. The P content of fresh preparations can be increased by phosphorylation even in the exercised muscle myosins up to the most higher level in human samples. The phosphoryl group incorporation from [gamma-32P]ATP into the rabbit and hare myosins was checked by radioactive tracer technique, and confirmed by total P content determination performed parallel with molybdate test. It was stated that under present circumstances the labelled 32P incorporation was lower even at an optimal substrate concentration than that of P value obtained directly with molybdate method; because the total P content of preparations had not exchanged during 2 min incubation. So it has been concluded from [gamma-23P] phosphoryl group assayments that much higher amount of P was incorporated into P-Arg, N pi-P-His and fraction 2 as compared with unappreciated labelled P level of the inorganic P (P-Ser, P-Thr), P-Lys, N tau-P-His and minor fractions. From these observations it has been considered that the P-Arg, N pi-P-His and fraction 2 take part in the contraction mechanism and in the course of physical training.
早期曾有关于肌球蛋白的自磷酸化以及兔骨骼肌不稳定磷酸盐（P）含量的报道[6, 7, 9]。本文描述了运动肌肉新鲜制剂中的内源性预形成P水平高于未训练对照肌肉。研究发现，在训练有素的人体肌肉制剂中存在大量线粒体肌球蛋白（其P含量高得多），这使得对肌原纤维肌球蛋白的评估出现偏差。因此，只有在线粒体部分分离后，才能从运动受试者中获得具有正确P含量的可靠肌原纤维制剂。即使在运动肌肉肌球蛋白中，新鲜制剂的P含量也可通过磷酸化增加，直至达到人体样本中的最高水平。通过放射性示踪技术检测了[γ-32P]ATP中磷酸基团掺入兔和野兔肌球蛋白的情况，并通过与钼酸盐试验平行进行的总P含量测定进行了确认。结果表明，在当前情况下，即使在最佳底物浓度下，标记的32P掺入量也低于直接用钼酸盐法获得的P值；因为制剂的总P含量在2分钟孵育期间没有交换。因此，从[γ-23P]磷酸基团测定得出结论，与无机P（P-丝氨酸、P-苏氨酸）、P-赖氨酸、N-τ-P-组氨酸和微量组分未被认识到的标记P水平相比，大量的P掺入了P-精氨酸、N-π-P-组氨酸和组分2中。基于这些观察结果，人们认为P-精氨酸、N-π-P-组氨酸和组分2参与了收缩机制以及体育训练过程。
