Levin R M, Longhurst P A, Levin S S, Haugaard N, Wein A J
Division of Urology, University of Pennsylvania School of Medicine, Philadelphia.
Mol Cell Biochem. 1990 Sep 21;97(2):153-9. doi: 10.1007/BF00221057.
The urinary bladder depends on intracellular ATP for the support of a number of essential intracellular processes including contraction. The concentration of ATP is maintained constant primarily via the rapid transfer of a phosphate from creatine phosphate (CP) to ADP catalyzed by the enzyme creatine kinase (CK). Since muscular pathologies associated with diabetes are in part related to intracellular alterations in metabolism, we have characterized the CK activity in both skeletal muscle and urinary bladder from control and streptozotocin-diabetic rats. The following is a summary of the results: 1) Bladder tissue from control rats showed linear kinetics with a Vmax = 390 nmoles/mg protein/min, and a Km = 275 microM. 2) Urinary bladder tissue isolated from diabetic rats displayed biphasic kinetics with Vmax = 65 and 324 nmoles/mg protein/min, and Km's = 10 microM and 190 microM respectively. 3) Skeletal muscle isolated from control rats showed linear kinetics with an approximate Vmax of 800 nmoles/mg protein/min and a Km of 280 microM CP. 4) Homogenates of skeletal muscle from diabetic rats showed complex kinetics not separable into distinct component forms. 5) The Km for ADP for both skeletal muscle and bladder was approximately 10 microM. These studies demonstrate that whereas bladders isolated from both control and diabetic rats possess a low-affinity isomer(s) of CK with similar maximum enzymatic activity, there is a high affinity isomer present within the urinary bladder muscle of diabetic rats that is not present in bladder tissue isolated from control rats. Skeletal muscle isolated from both diabetic and control rats exhibited a maximal activity 2 to 3 times higher than that of the bladder.
膀胱依赖细胞内三磷酸腺苷（ATP）来支持包括收缩在内的许多重要细胞内过程。ATP的浓度主要通过肌酸激酶（CK）催化的磷酸从磷酸肌酸（CP）快速转移至二磷酸腺苷（ADP）而维持恒定。由于与糖尿病相关的肌肉病变部分与细胞内代谢改变有关，我们已对对照大鼠和链脲佐菌素诱导的糖尿病大鼠的骨骼肌和膀胱中的CK活性进行了表征。以下是结果总结：1）对照大鼠的膀胱组织呈现线性动力学，Vmax = 390纳摩尔/毫克蛋白质/分钟，Km = 275微摩尔。2）从糖尿病大鼠分离的膀胱组织表现出双相动力学，Vmax分别为65和324纳摩尔/毫克蛋白质/分钟，Km分别为10微摩尔和190微摩尔。3）从对照大鼠分离的骨骼肌呈现线性动力学，近似Vmax为800纳摩尔/毫克蛋白质/分钟，CP的Km为280微摩尔。4）糖尿病大鼠骨骼肌匀浆表现出复杂动力学，无法分离成不同的组分形式。5）骨骼肌和膀胱中ADP的Km约为10微摩尔。这些研究表明，虽然从对照大鼠和糖尿病大鼠分离的膀胱都具有具有相似最大酶活性的低亲和力CK异构体，但糖尿病大鼠膀胱肌肉中存在一种对照大鼠分离的膀胱组织中不存在的高亲和力异构体。从糖尿病大鼠和对照大鼠分离的骨骼肌的最大活性比膀胱高2至3倍。
