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The plasmalemma redox system in unicellular green alga Dunaliella salina

Chen Sixue, Li Lin, Yan Jiqiong, Jiao Xinzhi

Shanghai Institute of Plant Physiology,The Chinese Academy of Sciences.Shanghhai 200032

Abstract

A plasmalemmma (PM)-bound redox system was identified in the unicellular green alga Dunalilla salina,which had the ability to oxidize exogenous NAD (P) H and to reduce Fe(CN)~(3-)_6and O_2.In the presence of Fe(CN)~(3-)_6,NADH was rapidly oxidized with a K_m of 96 #mu#mol/L,a V_max of 159 nmol 10~(-8) cells min~(-1) and an optimum pH of 8.5. Triton X-100 treatment greatly increased the redox activity of the cells in both NADH oxidation and Fe(CN)~(3-)_6 reduction. Exogenous NADH not only increased the activity of Fe(CN)~(3-)_6 reduction,but also stimulated O_2 consumption in a pH range from 5.6 to 9.6,with an optimum pH of 8.5.Without exogenous electron donor, the transmembrane Fe(CN)~(3-)_6 reduction could go on using the electrons from internal electron donors.The medium pH influenced the proportions of O_2 uptake through normal respiration pathway, altenative pathway and PM elecctron transport pathway.In the presence of NADH,SHAM stimulated O_2 uptake greatly,and O_2 consumption through PM electron transport pathway was also increased,especially at alkaline pH.The results suggested that the oxidase in the plasmalemma of D.salina had peroxidase properties and there might be two electron transport pathways.

Key words: Dunaliella salina;Redox system;O_(2) consumption;Respiration inhibitors

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Citing This Article：

Chen Sixue, Li Lin, Yan Jiqiong, Jiao Xinzhi. The plasmalemma redox system in unicellular green alga Dunaliella salina. Acta Physiol Sin 1996; 48 (2): (in Chinese with English abstract).