Barua M, Majumder G C
Indian Institute of Chemical Biology, Calcutta.
Biochem Cell Biol. 1987 Jul;65(7):602-9. doi: 10.1139/o87-080.
Intact washed spermatozoa from goat cauda epididymis possess an ecto-phosphoprotein phosphatase that causes dephosphorylation of phosphoserine and phosphothreonine residues of exogenous 32P-labelled histones. The cell-bound ecto-enzyme has high affinity for proteins (histones, casein, phosvitin, and protamine) rather than phosphate esters, such as p-nitrophenyl phosphate, beta-glycerophosphate, AMP, and ATP. The activity of the enzyme is inhibited by 4 mM Mg2+, Ca2+, Mn2+, or Co2+. Pi (10 mM), NaF (10 mM), and Zn2+ (1 mM) inhibit the enzyme by approximately 50, 35, and 100%, respectively. Polyamines such as spermine and spermidine at 10 mM each caused significant inhibition (60 and 30%, respectively) of the cell-bound phosphoprotein phosphatase activity, whereas cAMP, orthovanadate, and calmodulin (with or without Ca2+) had no appreciable effect. Under the standard assay conditions, spermatozoa remain intact as evidenced by assay of cytosolic enzyme markers. Both the washed and "native" intact spermatozoa showed nearly the same specific activity of the ectoenzyme. The product of the reaction (Pi) was found in the extracellular medium. Sonication doubled the enzymic activity of the intact cells. The specific activity of the enzyme was nearly fourfold higher in the intact forwardly motile cells than the "composite" spermatozoa. These data provide further support for the localization of a phosphoprotein phosphatase on the external surface of spermatozoa and that the ectoenzyme may have a role in the regulation of flagellar motility.
来自山羊附睾尾部的完整洗涤精子具有一种胞外磷蛋白磷酸酶，该酶可使外源32P标记组蛋白的磷酸丝氨酸和磷酸苏氨酸残基发生去磷酸化。这种细胞结合型胞外酶对蛋白质（组蛋白、酪蛋白、卵黄高磷蛋白和鱼精蛋白）具有高亲和力，而对磷酸酯如对硝基苯磷酸、β-甘油磷酸、AMP和ATP的亲和力较低。该酶的活性受到4 mM Mg2+、Ca2+、Mn2+或Co2+的抑制。Pi（10 mM）、NaF（10 mM）和Zn2+（1 mM）分别使该酶活性抑制约50%、35%和100%。10 mM浓度的精胺和亚精胺等多胺分别使细胞结合型磷蛋白磷酸酶活性受到显著抑制（分别为60%和30%），而cAMP、原钒酸盐和钙调蛋白（无论有无Ca2+）均无明显影响。在标准测定条件下，通过胞质酶标志物的测定证明精子保持完整。洗涤后的完整精子和“天然状态”的完整精子显示出几乎相同的胞外酶比活性。反应产物（Pi）存在于细胞外培养基中。超声处理使完整细胞的酶活性增加一倍。完整向前运动细胞中该酶的比活性比“混合”精子高近四倍。这些数据进一步支持了磷蛋白磷酸酶定位于精子外表面，且该胞外酶可能在鞭毛运动调节中起作用。
