杜氏盐藻细胞质膜氧化还原系统与K^+吸收

RELATIONSHIP OF PLASMALEMMA REDOX ACTIVITY TO K^+ UPTAKE BY DUNALIELLA SALINA CELLS

杜氏盐藻（Ｄｕｎａｌｉｅｌｌａ ｓａｌｉｎａ）细胞表面存在氧化ＮＡＤＨ 与还原Ｆｅ（ＣＮ）３－６ 的氧化还原系统（ｒｅｄｏｘｓｙｓｔｅｍ ）。该系统在氧化ＮＡＤＨ 时，抑制Ｋ＋ 的吸收，在还原Ｆｅ（ＣＮ）３－６ 时， 促进Ｋ＋ 的吸收，当ＮＡＤＨ 同时存在时， 促进效应最显著， 高达７３５％ 。外源ＮＡＤＨ 促进藻细胞的氧吸收达１６５％ ，而使胞质ｐＨ 下降； 当ＮＡＤＨ 存在时， Ｆｅ（ＣＮ）３－６ 被快速地还原， 同时藻细胞膜外酸化程度增加。质膜Ｈ＋ －ＡＴＰａｓｅ和氧化还原系统的典型抑制剂都不同程度地抑制Ｋ＋ 吸收； 并且钒酸盐对Ｋ＋ 吸收的抑制可以被加入ＮＡＤＨ 和Ｆｅ（ＣＮ）３－６ 而部分恢复， 表明质膜Ｈ＋ －ＡＴＰａｓｅ和氧化还原系统共同参与了细胞Ｋ＋

The plasmalemma bond redox system localized within the plasmalemma of unicellular green alga Dunaliella salina was studied.This system oxidized exogenous NADH,increased O 2 consumption to 165% and increased the pH of the external medium,while K + influx was inhibited.With no NADH added,ferricyanide stimulated K + uptake about 3 folds.In the presence of exogenous NADH,ferricyanide was rapidly reduced and the external medium was acidified,generating a greater electrochemical proton gradient across the plasmalemma,thus resulting an 6 fold increase of K + influx.Typical inhibitors of plasmalemma H + ATPase and redox system inhibited K + uptake to different extent.That the inhibition of K + uptake by vanadate could be resumed partly by addition of NADH and ferricyanide indicated that plasmalemma redox system operated in association with the H + ATPase to exert an influence on K + transportation.A model was presented in which the implication of two possible redox chains and H + ATPase in generating an electrochemical potential gradient for protons(ΔuH +) was discussed.