Ogilvie A, Antl W
J Biol Chem. 1983 Apr 10;258(7):4105-9.
Diadenosine tetraphosphatase, an enzyme splitting diadenosine tetraphosphate to AMP and ATP, has been purified to apparent homogeneity from a permanent cell line derived from a leukemic child. The purification procedure consisted of fractionation by ammonium sulfate precipitation, followed by Sephacryl 200 and DEAE-cellulose chromatography, and finally a differential membrane filtration. The enzyme is a single polypeptide chain of Mr = 17,500 as determined by gel electrophoresis in the presence of sodium dodecyl sulfate. The apparent molecular weight of the native enzyme was calculated as 20,000 from gel filtration data. The apparent Km for Ap4A was 0.5 microM as determined by two independent kinetic assays. None of the following compounds were substrates of the enzyme: diadenosine triphosphate, NAD, nucleoside 5'-phosphates (AMP, ATP, GDP, GTP, and UTP). The enzyme had optimal activity in the presence of 1 mM Mg2+, showing no activity in the presence of EDTA.
二腺苷四磷酸酶是一种将二腺苷四磷酸分解为AMP和ATP的酶，已从一名白血病儿童的永久性细胞系中纯化至表观均一。纯化过程包括硫酸铵沉淀分级，随后进行Sephacryl 200和DEAE-纤维素层析，最后进行差示膜过滤。通过十二烷基硫酸钠存在下的凝胶电泳测定，该酶是一条Mr = 17,500的单多肽链。根据凝胶过滤数据计算，天然酶的表观分子量为20,000。通过两种独立的动力学测定法确定，Ap4A的表观Km为0.5 microM。以下化合物均不是该酶的底物：二腺苷三磷酸、NAD、核苷5'-磷酸（AMP、ATP、GDP、GTP和UTP）。该酶在1 mM Mg2+存在下具有最佳活性，在EDTA存在下无活性。
