Brandão R L, Castro I M, Passos J B, Nicoli J R, Thevelein J M
Laboratório de Bioquímica e Fisiologia de Microorganismos, Escola de Farmácia, Universidade Federal de Ouro Preto, Brazil.
J Gen Microbiol. 1992 Aug;138 Pt 8:1579-86. doi: 10.1099/00221287-138-8-1579.
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 Km of about 3.2 mM for ATP whereas the activated enzyme showed an apparent Km 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.(ABSTRACT TRUNCATED AT 250 WORDS)
向尖孢镰刀菌亚麻变种的去阻遏细胞中添加葡萄糖和其他糖类，会在5分钟内引发质膜H(+) -ATP酶的激活。葡萄糖是最佳激活剂，而半乳糖和乳糖的作用较小。先前添加放线菌酮并不能阻止这种激活，去除葡萄糖后激活作用完全可逆。体内的激活过程也会导致该酶动力学性质的变化。未激活的酶对ATP的表观Km约为3.2 mM，而激活后的酶表观Km为0.26 mM。此外，H(+) -ATP酶的最适pH值在激活后从6.0变为7.5。激活后的酶对钒酸盐抑制更敏感。当尖孢镰刀菌在以葡萄糖为主要碳源的培养基中培养时，增强的H(+) -ATP酶活性主要局限于对应延滞期的阶段，即在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起始中起作用。向尖孢镰刀菌亚麻变种细胞中添加葡萄糖也会导致cAMP水平升高。其他糖类未显示出可靠的升高。在pH 5.0时添加质子载体如DNP和CCCP，会导致细胞内cAMP水平大幅升高以及质膜H(+) -ATP酶活性增强。吖啶橙抑制DNP诱导的cAMP水平升高，也会导致质膜H(+) -ATP酶激活受到抑制。（摘要截短于250字）
