大鼠脑线粒体NOS及L-Arg转运的生化特性

The biochemical properties of L-arginine/nitric oxide pathway in rat brain mitochondria

测定分离纯化的大鼠脑线粒体 (mitochondria ,Mt)L 精氨酸 (L arginine,L Arg) /一氧化氮合酶 (nitricoxidesynthase ,NOS) /NO系统 ,L Arg转运和NOS的活性。结果显示 :正常大鼠脑Mt膜上存在高亲和、低转运、可饱和的L Arg转运体。最大转运速率Vmax为 5 87± 0 4 6nmol/mgpro·min-1,米氏常数Km为 7 8± 0 5 6μmol/L。大鼠脑Mt在正常状态下仅有内皮型NOS (eNOS)表达。eNOS的最大活化速率Vmax为 2 7± 0 3 0nmol/mgpro·min-1,Km为2 0 85± 3 2 7μmol/L。Mt生成和释放NO 2 随孵育时间延长而增加 ,60min达峰值。结果提示 ,正常大鼠Mt膜上存在L Arg转运体 ,该转运体与细胞膜上Y+型氨基酸转运体相一致 ;MtNOS属eNOS MtL Arg/NOS/NO系统是细胞NO产生的来源之一。

Biochemical property of L arginine (L Arg)/nitric oxide synthase (NOS)/nitric oxide (NO) system was observed in rat brain mitochondria. The results showed that there existed L Arg transporters of high affinity, low transport and saturability in mitochondria membrane of normal rat brain. The maximum transport velocity (V max ) and Michaelis constant (Km) were 5 87±0 46 nmol/mg pro·min -1 and 7 8±0 56 μmol/L respectively. In normal condition, endothelium type NOS was expressed in the mitochondria of rat brain, with its V max and Km being 2 7±0 3 nmol/mg pro·min -1 and 20 85±3 27 μmol/L, respectively. NO production was increased in a time dependent manner and reached a maximum value at 60 min. These results suggest that the L Arg transporters in MT membrane of normal rat brain were similar with Y + type amino acid transporters in cellullar membrane. Furthermore the NOS of mitochondria belongs to eNOS, whereas the L Arg/NOS/NO system may be a source of NO.