Whitmarsh J, Cramer W A
Biochim Biophys Acta. 1977 May 11;460(2):280-9. doi: 10.1016/0005-2728(77)90214-6.
The kinetics of the photoreduction of cytochrome b-559 and plastoquinone were measured using well-coupled spinach chloroplasts. High potential (i.e, hydroquinone reducible) cytochrome b-559 was oxidized with low intensity far-red light in the presence of N-methyl phenazonium methosulfate or after preillumination with high intensity light. Using long flashes of red light, the half-reduction time of cytochrome b-559 was found to be 100 +/- 10 ms, compared to 6-10 ms for the photoreduction of the plastoquinone pool. Light saturation of the photoreduction of cytochrome b-559 occurred at a light intensity less than one-third of the intensity necessary for the saturation of ferricyanide reduction under identical illumination conditions. The photoreduction of cytochrome b-559 was accelerated in the presence of dibromothymoquinone with a t 1/2 = 25-35 ms. The addition of uncouplers, which caused stimulatory effect on ferricyanide reduction under the same experimental conditions resulted in a decrease in the rate of cytochrome b-559 reduction. The relatively slow photoreduction rate of cytochrome b-559 compared to the plastoquinone pool implies that electrons can be transferred efficiently from Photosystem II to plastoquinone without the involvement of cytochrome b-559 as an intermediate. These results indicate that it is unlikely that high potential cytochrome b-559 functions as an obligatory redox component in the main electron transport chain joining the two photosystems.
使用耦合良好的菠菜叶绿体测量了细胞色素b - 559和质体醌的光还原动力学。在存在N - 甲基硫酸吩嗪鎓的情况下，或在高强度光照预照射后，高电位（即可被对苯二酚还原的）细胞色素b - 559在低强度远红光下被氧化。使用长的红光闪光，发现细胞色素b - 559的半还原时间为100±10毫秒，而质体醌库的光还原时间为6 - 10毫秒。在相同光照条件下，细胞色素b - 559光还原的光饱和发生在光强度低于铁氰化物还原饱和所需强度的三分之一时。在二溴百里醌存在下，细胞色素b - 559的光还原加速，t1/2 = 25 - 35毫秒。在相同实验条件下对铁氰化物还原有刺激作用的解偶联剂的加入导致细胞色素b - 559还原速率降低。与质体醌库相比，细胞色素b - 559相对较慢的光还原速率意味着电子可以在不涉及细胞色素b - 559作为中间体的情况下从光系统II有效地转移到质体醌。这些结果表明，高电位细胞色素b - 559不太可能在连接两个光系统的主要电子传递链中作为必需的氧化还原组分起作用。
