GLUCOSE-INDUCED ACTIVATION OF THE PLASMA-MEMBRANE H+-ATPASE IN FUSARIUM-OXYSPORUM
GLUCOSE-INDUCED ACTIVATION OF THE PLASMA-MEMBRANE H+-ATPASE IN FUSARIUM-OXYSPORUM
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DOI：
10.1099/00221287-138-8-1579
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发表时间：
1992-08-01
期刊：
影响因子：
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通讯作者：
THEVELEIN, JM
中科院分区：
文献类型：
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作者：
BRANDAO, RL;CASTRO, IM;THEVELEIN, JM
将葡萄糖和其他糖添加到真菌镰刀菌（Fusarium oxysporum var. lini）的抑制细胞中，可在5分钟内激活质膜H+- atp酶。葡萄糖是最好的活化剂，而半乳糖和乳糖的作用较小。先前添加的环己亚胺并没有阻止活化，当葡萄糖被去除时，它是完全可逆的。体内的活化过程也引起酶动力学性质的变化。未激活的酶对ATP的表观K(m)约为3.2 mM，而激活的酶对ATP的表观K(m)为0.26 mM。此外，H+-ATP酶在活化后的最适pH由6.0变为7.5。活化酶对钒酸盐的抑制更为敏感。当尖孢镰刀菌在以葡萄糖为主要碳源的培养基中培养时，H+- atp酶活性的增强主要局限于滞后期对应的时期，即培养基酸化开始之前。这表明激活过程可能在细胞外酸化的发生中起作用。在尖孢镰刀菌细胞中添加葡萄糖也能引起cAMP水平的升高。其他糖类没有可靠的增加。在pH 5.0下加入质子离子载体如DNP和CCCP，可使胞内cAMP水平和质膜H+- atp酶活性大幅增加。吖啶橙抑制dnp诱导的cAMP水平升高，也抑制了质膜H+- atp酶的激活。这些结果提示，尖孢弧菌（F. oxysporum var. lini）质膜H+- atp酶活性与胞内cAMP水平之间可能存在因果关系。
Addition of glucose and other sugars to derepressed cells of the fungus Fusarium oxysporum var. lini triggered activation of the plasma membrane H+-ATPase within 5 min. Glucose was the best activator while galactose and lactose had a lesser effect. The activation was not prevented by previous addition of cycloheximide and it was fully reversible when the glucose was removed. The activation process in vivo also caused changes in the kinetic properties of the enzyme. The non-activated enzyme had an apparent K(m) of about 3.2 mM for ATP whereas the activated enzyme showed an apparent K(m) of 0.26 mM. In addition, the pH optimum of the H+-ATPase changed from 6.0 to 7.5 upon activation. The activated enzyme was more sensitive to inhibition by vanadate. When F. oxysporum was cultivated in media containing glucose as the major carbon source, enhanced H+-ATPase activity was largely confined to the period corresponding to the lag phase, i.e. just before the start of acidification of the medium. This suggests that the activation process might play a role in the onset of extracellular acidification. Addition of glucose to F. oxysporum var. lini cells also caused an increase in the cAMP level. No reliable increase could be demonstrated for the other sugars. Addition of proton ionophores such as DNP and CCCP at pH 5.0 caused both a large increase in the intracellular level of cAMP and in the activity of the plasma membrane H+-ATPase. Inhibition of the DNP-induced increase in the cAMP level by acridine orange also resulted in inhibition of the activation of plasma membrane H+-ATPase. These results suggest a possible causal relationship between the activity of F. oxysporum var. lini plasma membrane H+-ATPase and the intracellular level of cAMP.