Ronquist G
Department of Clinical Chemistry, University Hospital, Uppsala, Sweden.
Urol Int. 1988;43(6):334-40. doi: 10.1159/000281386.
A stimulation by zinc ions of the hydrolysis of ATP by prostasomes prepared from human semen has been observed. Stimulation was maximal at a Zn2+/ATP stoichiometry of 0.5/l, and increasing this ratio resulted in a gradual decrease in ATPase activity. The pH optimum was 6.0. The apparent Km for Zn2+-dependent ATPase was 0.43 mmol/l and apparent Vmax 5.60 mumol/mg protein/20 min. Other divalent cations could replace Zn2+ as cofactor more or less effectively in the order Mn2+ greater than Cd2+ greater than Ba2+ greater than Sr2+. Potassium ions produced a further activation of the Zn2+-dependent ATPase system by about 10%. Such a stimulation was also attained to some extent by other monovalent cations as Rb+, NH4+, Li+ and to a lesser extent by Cs+. Orthovanadate in the concentration interval 5-1,000 mumol/l was inhibitory of the Zn2+-dependent ATPase system in a dose-dependent fashion. An aminopeptidase activity was also linked to the prostasomes. This enzyme activity was dramatically inhibited by 2 mmol/l orthophenantroline. A reactivation of the orthophenantroline-inhibited aminopeptidase activity was possible by adding Zn2+ to the reaction mixture. Hence, prostasomes contained ATPase as well as aminopeptidase activities both of which being dependent upon Zn2+. These two activities did not seem to be expressions of an ATP-dependent protease activity associated with prostasomes.
已观察到锌离子对从人精液制备的前列腺小体水解ATP有刺激作用。在Zn²⁺/ATP化学计量比为0.5/1时刺激作用最大，增加该比例会导致ATP酶活性逐渐降低。最适pH为6.0。依赖锌离子的ATP酶的表观Km为0.43 mmol/l，表观Vmax为5.60 μmol/mg蛋白质/20分钟。其他二价阳离子可以或多或少有效地替代Zn²⁺作为辅因子，顺序为Mn²⁺＞Cd²⁺＞Ba²⁺＞Sr²⁺。钾离子使依赖锌离子的ATP酶系统进一步激活约10%。其他单价阳离子如Rb⁺、NH₄⁺、Li⁺在一定程度上也能产生这种刺激，而Cs⁺的刺激程度较小。浓度在5 - 1000 μmol/l区间的原钒酸盐以剂量依赖方式抑制依赖锌离子的ATP酶系统。一种氨肽酶活性也与前列腺小体相关。该酶活性被2 mmol/l邻菲罗啉显著抑制。通过向反应混合物中添加Zn²⁺，可以使被邻菲罗啉抑制的氨肽酶活性重新激活。因此，前列腺小体含有ATP酶和氨肽酶活性，两者均依赖于Zn²⁺。这两种活性似乎不是与前列腺小体相关的ATP依赖性蛋白酶活性的表现。
