Bennett A B, O'neill S D, Eilmann M, Spanswick R M
Section of Plant Biology, Division of Biological Sciences, Cornell University, Ithaca, New York 14853.
Plant Physiol. 1985 Jul;78(3):495-9. doi: 10.1104/pp.78.3.495.
Two distinct membrane fractions containing H(+)-ATPase activity were prepared from red beet. One fraction contained a H(+)-ATPase activity that was inhibited by NO(3) (-) while the other contained a H(+)-ATPase inhibited by vanadate. We have previously proposed that these H(+)-ATPases are associated with tonoplast (NO(3) (-)-sensitive) and plasma membrane (vanadate-sensitive), respectively. Both ATPase were examined to determine to what extent their activity was influenced by variations in the concentration of ATPase substrates and products. The substrate for both ATPase was MgATP(2-), and Mg(2+) concentrations in excess of ATP had only a slight inhibitory effect on either ATPase. Both ATPases were inhibited by free ATP (i.e. ATP concentrations in excess of Mg(2+)) and ADP but not by AMP. The plasma membrane ATPase was more sensitive than the tonoplast ATPase to free ATP and the tonoplast ATPase was more sensitive than the plasma membrane ATPase to ADP.Inhibition of both ATPases by free ATP was complex. Inhibition of the plasma membrane ATPase by ADP was competitive whereas the tonoplast ATPase demonstrated a sigmoidal dependence on MgATP(2-) in the presence of ADP. Inorganic phosphate moderately inhibited both ATPases in a noncompetitive manner.Calcium inhibited the plasma membrane but not the tonoplast ATPase, apparently by a direct interaction with the ATPase rather than by disrupting the MgATP(2-) complex.The sensitivity of both ATPases to ADP suggests that under conditions of restricted energy supply H(+)-ATPase activity may be reduced by increases in ADP levels rather than by decreases in ATP levels per se. The sensitivity of both ATPases to ADP and free ATP suggests that modulation of cytoplasmic Mg(2+) could modulate ATPase activity at both the tonoplast and plasma membrane.
从红甜菜中制备了两种含有H(+)-ATP酶活性的不同膜组分。一种组分含有受NO(3) (-)抑制的H(+)-ATP酶活性，而另一种含有受钒酸盐抑制的H(+)-ATP酶。我们之前曾提出，这些H(+)-ATP酶分别与液泡膜（对NO(3) (-)敏感）和质膜（对钒酸盐敏感）相关。对这两种ATP酶进行了检测，以确定它们的活性在多大程度上受到ATP酶底物和产物浓度变化的影响。两种ATP酶的底物都是MgATP(2-)，ATP过量时的Mg(2+)浓度对任何一种ATP酶都只有轻微的抑制作用。两种ATP酶都受到游离ATP（即ATP浓度超过Mg(2+)）和ADP的抑制，但不受AMP的抑制。质膜ATP酶比液泡膜ATP酶对游离ATP更敏感，而液泡膜ATP酶比质膜ATP酶对ADP更敏感。游离ATP对两种ATP酶的抑制作用很复杂。ADP对质膜ATP酶的抑制是竞争性的，而在有ADP存在时，液泡膜ATP酶对MgATP(2-)表现出S形依赖性。无机磷酸盐以非竞争性方式适度抑制两种ATP酶。钙抑制质膜ATP酶，但不抑制液泡膜ATP酶，显然是通过与ATP酶直接相互作用，而不是通过破坏MgATP(2-)复合物。两种ATP酶对ADP的敏感性表明，在能量供应受限的情况下，H(+)-ATP酶活性可能会因ADP水平升高而降低，而不是因ATP水平本身降低。两种ATP酶对ADP和游离ATP的敏感性表明，细胞质Mg(2+)的调节可以调节液泡膜和质膜上的ATP酶活性。
