Department of Biochemistry, The Connecticut Agricultural Experiment Station, P. O. Box 1106, New Haven, Connecticut 06504.
Plant Physiol. 1978 Dec;62(6):938-40. doi: 10.1104/pp.62.6.938.
The addition of glyoxylate to tobacco (Nicotiana tabacum) leaf discs inhibited glycolate synthesis and photorespiration and increased net photosynthetic (14)CO(2) fixation. This inhibition of photorespiration was investigated further by studying the effect of glyoxylate on the stimulation of photosynthesis that occurs when the atmospheric O(2) level was decreased from 21 to 3% (the Warburg effect). The Warburg effect is usually ascribed to the increased glycolate synthesis and metabolism that occurs at higher O(2) concentrations. Photosynthesis in control discs increased from 59.1 to 94.7 micromoles of CO(2) per gram fresh weight per hour (a 60% increase) when the O(2) level was lowered from 21 to 3%, while the rate for discs floated on 15 millimolar glyoxylate increased only from 82.0 to 99.7 micromoles of CO(2) per gram fresh weight per hour (a 22% increase). The decrease in the O(2) sensitivity of photosynthesis in the presence of glyoxylate was explained by changes in the rate of glycolate synthesis under the same conditions.The rate of metabolism of the added glyoxylate by tobacco leaf discs was about 1.35 micromoles per gram fresh weight per hour and was not dependent on the O(2) concentration in the atmosphere. This rate of metabolism is about 10% the amount of stimulation in the rate of CO(2) fixation caused by the glyoxylate treatment on a molar carbon basis. Glyoxylate (10 millimolar) had no effect on the carboxylase/oxygenase activity of isolated ribulose diphosphate carboxylase. Although the biochemical mechanism by which glyoxylate inhibits glycolate synthesis and photorespiration and thereby decreases the Warburg effect is still uncertain, these results show that cellular metabolites can regulate the extent of the Warburg effect.
草酰乙酸的添加抑制了烟草（Nicotiana tabacum）叶片的乙醛酸合成和光呼吸作用，增加了净光合（14）CO2 固定。通过研究草酰乙酸对光合作用的刺激效应，进一步研究了这种光呼吸抑制作用，当大气中的 O2 水平从 21%降低到 3%时，就会发生光合作用的刺激效应（Warburg 效应）。通常，Warburg 效应归因于在较高 O2 浓度下发生的乙醛酸合成和代谢的增加。在对照盘片中，当 O2 水平从 21%降低到 3%时，光合作用从 59.1 增加到 94.7 微摩尔 CO2/克鲜重/小时（增加 60%），而在 15 毫摩尔草酰乙酸上漂浮的盘片的速率仅从 82.0 增加到 99.7 微摩尔 CO2/克鲜重/小时（增加 22%）。在存在草酰乙酸的情况下，光合作用对 O2 敏感性的降低可以通过在相同条件下乙醛酸合成速率的变化来解释。烟草叶片盘片对添加草酰乙酸的代谢速率约为 1.35 微摩尔/克鲜重/小时，且不依赖于大气中的 O2 浓度。以摩尔碳为基础，该代谢速率约为草酰乙酸处理引起的 CO2 固定速率刺激的 10%。10 毫摩尔草酰乙酸对分离的核酮糖二磷酸羧化酶/加氧酶的活性没有影响。尽管草酰乙酸抑制乙醛酸合成和光呼吸作用从而降低 Warburg 效应的生化机制尚不确定，但这些结果表明细胞代谢物可以调节 Warburg 效应的程度。
