Rodriguez del Castillo A, Torres M, Delicado E G, Miras-Portugal M T
Departamento de Bioquimica, Facultad de Medicina, Universidad de la Laguna, Islas Canarias, Spain.
J Neurochem. 1988 Dec;51(6):1696-703. doi: 10.1111/j.1471-4159.1988.tb01147.x.
Diadenosine tetraphosphate (Ap4A) and diadenosine pentaphosphate (Ap5A) have been identified in bovine adrenal medullary tissue using an HPLC method. The values obtained were 0.1 +/- 0.05 mumol/g of tissue for both compounds. The subcellular fraction where Ap4A and Ap5A were present in the highest concentration was chromaffin granules: 32 nmol/mg of protein for both compounds (approximately 6 mM intragranularly). This value was 30 times higher than in the cytosolic fraction. Enzymatic degradation of Ap4A and Ap5A, isolated from chromaffin granules, with phosphodiesterase produces AMP as the final product. The Ap4A and Ap5A obtained from this tissue were potent inhibitors of adenosine kinase. Their Ki values relative to adenosine were 0.3 and 2 microM for Ap4A and Ap5A, respectively. The cytosolic fraction also contains enzymatic activities that degrade Ap4A as well as Ap5A. These activities were measured by an HPLC method; the observed Km values were 10.5 +/- 0.5 and 13 +/- 1 microM for Ap4A and Ap5A, respectively.
已使用高效液相色谱法在牛肾上腺髓质组织中鉴定出四磷酸二腺苷（Ap4A）和五磷酸二腺苷（Ap5A）。两种化合物的测得值均为0.1±0.05 μmol/g组织。Ap4A和Ap5A浓度最高的亚细胞部分是嗜铬颗粒：两种化合物均为32 nmol/mg蛋白质（颗粒内约6 mM）。该值比胞质部分高30倍。从嗜铬颗粒中分离出的Ap4A和Ap5A用磷酸二酯酶进行酶促降解，最终产物为AMP。从该组织中获得的Ap4A和Ap5A是腺苷激酶的有效抑制剂。它们相对于腺苷的Ki值，Ap4A为0.3 μM，Ap5A为2 μM。胞质部分也含有降解Ap4A和Ap5A的酶活性。这些活性通过高效液相色谱法测量；观察到的Ap4A和Ap5A的Km值分别为10.5±0.5 μM和13±1 μM。
