弱有机碱对光合磷酸化的影响

Effects of Weak Organic Bases on Photophosphorylation

类囊体内部介质可被弱有机碱如吡啶、苯胺、咪唑缓冲,致使[H_(in)^+] 减少,ΛpH幅度降低,光合磷酸化(PSP)反应被抑制,对苯二胺(p—PD)降低ΛpH,但显著促进PSP反应、在MV或PMS系统中均有此现象;在 MV+DBMIB;MV+DCMU或PMS+DBMIB系统中,p—PDH_2重建ΛpH并恢复PSP反应活力。从p—PD(H_2)既具有弱有机碱性质,又可作为电子供体、氢递体,代替QH_2或PQH_2调节电子传递起转移质子的两种作用,解释了p—PD对ΛpH的抑制,却又促进PSP反应的现象。讨论了PSP反应对[H_(in)^+],ΛpH幅度大小的依赖关系。

We studied the effects of changing the inter-vial proton buffer capacity of thylakoid on ΔpHand photophosphorylation (PSP) in steady state bypenetrating weak organic bases, such as pyridine,aniline, imidazole and p-phenylene diamine intothylakoid lumen. The results were as follows: 1. The internal medium of the thylakoidwas buffered by pyridine, aniline and imidozole,and thus the thylakoid internal proton concen-tration was decreased, the magnitude of ΔpHand PSP activity were inhibited consequently(Fig. 1, 2). 2. Under the action of penetrating p-phe-nylene diamine the magnitude of ΔpH wasdecreased, but PSP reaction was stimulated sig-nificantly in MV noncyclic or PMS cyclic sys-tems. (Fig. 4, 5). 3. In MV+ DBMIB, MV+ DCMU or PMS+DBMIB systems we observed that the ΔpHand PSP reaction could be reconstructed or res-tored by reduccd p-phenylene diamine (p-PDH_2)(Fig. 7, 8). 4. The rate of electron transport was stimu-ated by p-PD (Fig. 6), this became the cause ofthe stimulation of PSP by p-PD. p-PDH_2 couldact as an electron donor and proton carrier, so itcould regulate electron transport and translocateproton across the membrane in stead of QH_2or PDH_2. Besides, p-PD had a property of weakorganic bases. Therefore, these could be usedto elucidate the inhibition of ΔpH and stimula-tion of PSP reaction by p-PD. It indicated fromthe action of weak organic bases that PSP reac-tion was dependent on the [H_(?n)^+] and amplitudeof ΔpH.