Elzainy T A, Ali T H
Department of Microbial Chemistry, National Research Center, Dokki, Cairo, Egypt.
Biochim Biophys Acta. 1995 Oct 4;1239(1):91-7. doi: 10.1016/0005-2736(95)00118-m.
Extracts of A. niger could catalyze sequential hydrolysis of the three phosphate moieties of the ATP molecule optimally at pH 2 and at pH 8. At pH 2 the hydrolysis was effected by an ATPase followed by acid phosphatase while at pH 8 alkaline phosphatase was the only involved enzyme. Separation of these three phosphate-hydrolyzing enzymes was achieved by Sephadex G-100 column chromatography. The A. niger ATPase seems to have two unique features. First, it was easily solubilized in distilled water and second it had optimum activity at pH 2. The activity of this enzyme was not affected on addition of Na+, K+ or Ca2+ to the assay reaction mixture. It was neither inhibited by sodium azide nor by potassium nitrate but inhibited by orthovanadate, DES, DCCD, Mg2+ and Pi. The substrate concentration-activity relationship was of the hyperbolic type. The enzyme had high specificity for ATP, was inert with ADP and its activity with GTP represented about 6% only of that obtained with equimolar amount of ATP.
黑曲霉提取物能够在pH 2和pH 8时最优地催化ATP分子的三个磷酸基团的顺序水解。在pH 2时，水解由一种ATP酶接着酸性磷酸酶进行，而在pH 8时，碱性磷酸酶是唯一涉及的酶。通过葡聚糖G - 100柱色谱法实现了这三种磷酸水解酶的分离。黑曲霉ATP酶似乎有两个独特的特征。第一，它很容易溶解于蒸馏水中；第二，它在pH 2时有最优活性。向测定反应混合物中添加Na⁺、K⁺或Ca²⁺不会影响该酶的活性。它既不被叠氮化钠抑制，也不被硝酸钾抑制，但会被原钒酸盐、二乙基亚砜（DES）、二环己基碳二亚胺（DCCD）、Mg²⁺和无机磷酸盐（Pi）抑制。底物浓度 - 活性关系呈双曲线型。该酶对ATP具有高度特异性，对ADP无活性，其对GTP的活性仅约为等摩尔量ATP所获得活性的6%。
