Rodriguez-Pascual F, Torres M, Rotllán P, Miras-Portugal M T
Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain.
Arch Biochem Biophys. 1992 Aug 15;297(1):176-83. doi: 10.1016/0003-9861(92)90657-i.
An ectoenzyme hydrolyzing diadenosine polyphosphates (ApnA) to AMP and Ap(n-1) has been studied in cultured chromaffin cells from bovine adrenal medulla. The KM value for extracellular Ap4A hydrolysis was 2.90 +/- 0.72 microM, the V(max) value obtained was 11.59 +/- 0.92 pmol/min x 10(6) cells (116 pmol/min.mg total protein). Ap3A, Ap5A, Ap6A, and Gp4G were competitive inhibitors of Ap4A hydrolysis with K(i) values of 3.65, 1.10, 1.20, and 2.65 microM, respectively. Phosphatidylinositol-specific phospholipase C removes the ApnA hydrolase activity from cultured chromaffin cells, suggesting an anchorage of this protein to the plasma membrane through the phosphatidylinositol. The turnover time for this enzyme calculated in the presence of cycloheximide was 38.94 +/- 1.53 hr for cultured chromaffin cells.
已对一种将二腺苷多磷酸（ApnA）水解为AMP和Ap(n - 1)的胞外酶进行了研究，该酶来自牛肾上腺髓质的培养嗜铬细胞。细胞外Ap4A水解的KM值为2.90±0.72微摩尔，获得的V(max)值为11.59±0.92皮摩尔/分钟×10(6)个细胞（116皮摩尔/分钟·毫克总蛋白）。Ap3A、Ap5A、Ap6A和Gp4G是Ap4A水解的竞争性抑制剂，其K(i)值分别为3.65、1.10、1.20和2.65微摩尔。磷脂酰肌醇特异性磷脂酶C可去除培养嗜铬细胞中的ApnA水解酶活性，这表明该蛋白通过磷脂酰肌醇锚定在质膜上。在存在环己酰亚胺的情况下，计算得出该酶在培养嗜铬细胞中的周转时间为38.94±1.53小时。
