MANIPULATING CYTOPLASMIC PH UNDER ANOXIA - A CRITICAL TEST OF THE ROLE OF PH IN THE SWITCH FROM AEROBIC TO ANAEROBIC METABOLISM
MANIPULATING CYTOPLASMIC PH UNDER ANOXIA - A CRITICAL TEST OF THE ROLE OF PH IN THE SWITCH FROM AEROBIC TO ANAEROBIC METABOLISM
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DOI：
10.1007/bf00202588
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发表时间：
1995-01-01
期刊：
影响因子：
4.3
通讯作者：
RATCLIFFE, RG
中科院分区：
文献类型：
--
作者：
FOX, GG;MCCALLAN, NR;RATCLIFFE, RG
玉米（Zea mays L.）根尖的乙醇产量，通过悬浮培养基的酶测定，与细胞质pH的变化相关，通过体内P-31核磁共振（NMR）波谱测定，在缺氧开始后。通过以下方法获得了细胞质pH在触发缺氧条件下乙醇生产转换中的作用的有力证据：(i)在pH 4和pH 10之间改变悬浮介质的pH；（ii）利用渗透的弱碱甲胺来对抗缺氧条件引起的细胞质酸化。实验证明，在pH稳定后，在缺氧条件下操纵细胞质pH要容易得多，而不是在缺氧开始后发生的最初快速酸化期间，在甲胺的存在下，有可能在缺氧代谢的组织上施加正常的需氧细胞质pH值。通过这种方法，可以证明缺氧条件下pH对乙醇生产影响的可逆性，从而为缺氧反应的生化pH-stat模型提供了很好的证据。在甲胺存在的情况下，胞质pH的核磁共振测量是通过使用锰预处理技术来消除胞质和液泡P-i信号之间的干扰来实现的，并且这里使用的实验方法似乎有可能在缺氧代谢反应的研究中有进一步的应用。
Ethanol production by maize (Zea mays L.) root tips, measured by an enzymic assay of the suspending medium, was correlated with changes in the cytoplasmic pH, determined by in-vivo P-31 nuclear magnetic resonance (NMR) spectroscopy, following the onset of anoxia. Strong evidence for the role of the cytoplasmic pH in triggering the switch to ethanol production under anoxia was obtained by: (i) varying the pH of the suspending medium between pH 4 and pH 10; and (ii) using the permeant weak base methylamine to combat the acidification of the cytoplasm induced by the anoxic conditions. Experimentally, it proved to be much easier to manipulate the cytoplasmic pH under anoxia after the pH had stabilised, rather than during the initial rapid acidification that occurred following the onset of anoxia, and in the presence of methylamine, it was possible to impose a normal aerobic cytoplasmic pH value on tissue that was metabolising anaerobically. By this means it was possible to demonstrate the reversibility of the pH effect on ethanol production under anoxia and thus to provide good evidence in support of the biochemical pH-stat model of the anoxic response. The NMR measurement of the cytoplasmic pH in the presence of methylamine was achieved by using a manganese pretreatment technique to eliminate interference between the cytoplasmic and vacuolar P-i signals, and it seems likely that the experimental approach used here will have further applications in studies of the metabolic response to anoxia.