Majumder G C
Biochem J. 1981 Apr 1;195(1):103-10. doi: 10.1042/bj1950103.
Ecto-ATPase in rat cauda-epididymal intact spermatozoa has a high degree of substrate specificity for the hydrolysis of ATP and dATP rather than of ADP, AMP, GTP, dGTP, CTP, dCTP, TTP and UTP. The enzyme is activated by bivalent metal ions in the order Mg2+ greater than Mn2+ greater than Co2+ greater than Ca2+. The apparent Km values of the enzyme for Mg2+, Mn2+, Co2+ and Ca2+ are approx. 80, 100, 100 and 150 microM respectively. Addition of Ca2+ (0.1 or 1 mM) gives no further stimulation of the Mg2+-activated ecto-ATPase activity. The apparent Km value of the enzyme for ATP is 95 microM. Pi (16 mM) inhibits the enzymic activity (by 25%), whereas Na+ (50 mM) or K+ (10 mM) alone or in combination, polyamines (spermine and spermidine; 1--12.5mM) and nucleic acids (yeast RNA and calf thymus DNA; 0.12 or 0.62 mg/ml) had no significant effect on the activity of the enzyme. Orthovanadate at a relatively low concentration (20 microM) strongly inhibits (approx. 50%) the ecto-ATPase activity. Vanadate inhibition can be reversed by noradrenaline (2.5 mM). The vanadate-sensitivity of the enzyme increases markedly during spermatozoal maturation in the epididymis. However, the activity of the spermatozoal ecto-ATPase decreases progressively during the epididymal transit of the testicular spermatozoa.
大鼠附睾尾完整精子中的胞外ATP酶对ATP和dATP的水解具有高度的底物特异性，而对ADP、AMP、GTP、dGTP、CTP、dCTP、TTP和UTP则不然。该酶被二价金属离子激活，其顺序为Mg2+＞Mn2+＞Co2+＞Ca2+。该酶对Mg2+、Mn2+、Co2+和Ca2+的表观Km值分别约为80、100、100和150μM。添加Ca2+（0.1或1 mM）不会进一步刺激Mg2+激活的胞外ATP酶活性。该酶对ATP的表观Km值为95μM。Pi（16 mM）抑制酶活性（25%），而单独或联合使用的Na+（50 mM）或K+（10 mM）、多胺（精胺和亚精胺；1--12.5 mM）以及核酸（酵母RNA和小牛胸腺DNA；0.12或0.62 mg/ml）对酶活性没有显著影响。相对低浓度（20μM）的原钒酸盐强烈抑制（约50%）胞外ATP酶活性。去甲肾上腺素（2.5 mM）可逆转钒酸盐抑制作用。在附睾中精子成熟过程中，该酶对钒酸盐的敏感性显著增加。然而，睾丸精子在附睾转运过程中，精子胞外ATP酶的活性逐渐降低。
