平滑肌肌球蛋白磷酸化与肌动球蛋白功能调节

在有Ｃａ２＋和钙调蛋白存在时，肌球蛋白轻链激酶催化肌球蛋白磷酸化，促使肌动蛋白激活的肌球蛋白（肌动球蛋白）Ｍｇ２＋－ＡＴＰ酶活性显著增加．然而，肌球蛋白磷酸化水平与Ｍｇ２＋－ＡＴＰ酶之间的关系是非线性的，原肌球蛋白可以进一步增加Ｍｇ２＋－ＡＴＰ酶的活性，但仍不改变它们之间的非线性关系．肌球蛋白轻链激酶的合成肽抑制剂抑制了肌球蛋白磷酸化和Ｍｇ２＋－ＡＴＰ酶活性，并导致平滑肌去膜肌纤维的等长收缩张力与速度的降低．结果提示肌球蛋白轻链激酶参与脊椎动物平滑肌收缩的调节过程，肌球蛋白轻链磷酸化作用会引起平滑肌收缩

Phosphorylation of Myosin and Regulation of Actomyosin Function in Smooth Muscle

In the presence of Ca 2 and calmodulin,the smooth muscle myosin can be phosphorylated by myosin light chain kinase and actin activated myosin Mg 2 ATPase activity obviously increases.However,relationship between myosin phosphorylation level and Mg 2 ATPase activity exhibits non linear.Tropomyosin can further enhance Mg 2 ATPase activity,but do not change their non linear relationship.A synthetic peptide inhibitor (22 amino acid peptide)of myosin light chain kinase inhibits myosin phosphorylation and actin activated myosin Mg 2 ATPase,leading to reduce the isometric tenion and velocity of the skinned smooth muscle fibers.It is suggested that myosin light chain kinase might participate in regulatory process and phosphorylation of myosin light chain would be required for initiation of smooth muscle contraction from vertebrate.