Dahlmann N, Kirchgesser M
Institut für Klinische Biochemie, Bonn, FRG.
Biochem Int. 1990;20(2):317-27.
Acid nucleoside triphosphatase (Acid NTPase), an enzyme which catalyzes the hydrolysis of all nucleoside triphosphates to the corresponding diphosphates was purified from human serum with a purification factor of 190 and a recovery of 31%. The molecular weight was 75,000 as estimated by gel filtration. Gel-electrophoresis revealed an Rf-value of 0.11, and the isoelectric point was determined at pH 4.4. It exhibited a temperature optimum of 44 degrees C and the activation energy was estimated to be 41.6 kJ/mol. The enzyme was active in the absence of divalent cations, since activity was not inhibited by EDTA. The presence of this chelator reduced the Km-value from 70 to 40 microM. Inhibitor experiments revealed that tartrate was a weak mixed-type noncompetitive inhibitor, Ki = 88 mM. The enzyme was specific for the hydrolysis of nucleoside triphosphates. P-nitrophenyl phosphate was not accepted as a substrate. The enzyme revealed optimum activity at the exceptionally acid pH of 3.0. These unique characteristics indicate the presence of a novel enzyme.
酸性核苷三磷酸酶（酸性NTP酶）是一种催化所有核苷三磷酸水解为相应二磷酸的酶，从人血清中纯化得到，纯化因子为190，回收率为31%。通过凝胶过滤估计其分子量为75,000。凝胶电泳显示Rf值为0.11，等电点测定为pH 4.4。其最适温度为44℃，活化能估计为41.6 kJ/mol。该酶在没有二价阳离子的情况下也有活性，因为其活性不受EDTA抑制。这种螯合剂的存在使Km值从70 μM降至40 μM。抑制剂实验表明，酒石酸盐是一种弱混合型非竞争性抑制剂，Ki = 88 mM。该酶对核苷三磷酸的水解具有特异性。对硝基苯磷酸不被接受为底物。该酶在异常酸性的pH 3.0下显示出最佳活性。这些独特的特性表明存在一种新型酶。
