Laboratory of Biophysics, School of Biological Sciences, Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea.
Laboratory of Biophysics, School of Biological Sciences, Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea.
Biochim Biophys Acta Gen Subj. 2018 Jan;1862(1):18-39. doi: 10.1016/j.bbagen.2017.10.003. Epub 2017 Oct 7.
High methylglyoxal content disrupts cell physiology, but mammals have scavengers to prevent glycolytic and mitochondrial dysfunctions. In yeast, methylglyoxal accumulation triggers methylglyoxal-oxidizing alcohol dehydrogenase (Adh1) activity. While methylglyoxal reductases and glyoxalases have been well studied in prokaryotes and eukaryotes, experimental evidence for methylglyoxal dehydrogenase (Mgd) and other catalytic activities of this enzyme affecting glycolysis and the tricarboxylic acid cycle is lacking.
A glycine-rich cytoplasmic Mgd protein, designated as Mgd1/Grp2, was isolated from glutathione-depleted Candida albicans. The effects of Mgd1/Grp2 activities on metabolic pathophysiology were investigated using knockout and overexpression mutants. We measured glutathione-(in)dependent metabolite contents and metabolic effects, including viability, oxygen consumption, ADH1 transcripts, and glutathione reductase and α-ketoglutarate dehydrogenase activities in the mutants. Based on the findings, methylglyoxal-oxidizing proteins were monitored to determine effects of MGD1/GRP2 disruption on methylglyoxal-scavenging traits during glutathione deprivation.
Methylglyoxal-oxidizing NAD(H)-linked Mgd1/Grp2 was found solely in glutathione auxotrophs, and it catalyzed the reduction of both methylglyoxal and pyruvate. MGD1/GRP2 disruptants showed growth defects, cell-cycle arrest, and methylglyoxal and pyruvate accumulation with mitochondrial impairment, regardless of ADH1 compensation. Other methylglyoxal-oxidizing enzymes were identified as key glycolytic enzymes with enhanced activity and transcription in MGD1/GRP2 disruptants, irrespective of glutathione content.
Failure of methylglyoxal and pyruvate dissimilation by Mgd1/Grp2 deficiency leads to poor glutathione-dependent redox regulation despite compensation by Adh1.
This is the first report that multifunctional Mgd activities contribute to scavenging methylglyoxal and pyruvate to maintain metabolic homeostasis and the redox pool via glycolytic enzymes and Adh1 expression.
高甲基乙二醛含量会破坏细胞生理机能，但哺乳动物有清除剂来防止糖酵解和线粒体功能障碍。在酵母中，甲基乙二醛的积累会触发甲基乙二醛氧化型醇脱氢酶（Adh1）的活性。虽然在原核生物和真核生物中，甲基乙二醛还原酶和甘油醛酶已得到了很好的研究，但缺乏关于甲基乙二醛脱氢酶（Mgd）和该酶其他催化活性影响糖酵解和三羧酸循环的实验证据。
从谷胱甘肽耗尽的白色念珠菌中分离出一种富含甘氨酸的细胞质 Mgd 蛋白，命名为 Mgd1/Grp2。通过敲除和过表达突变体研究了 Mgd1/Grp2 活性对代谢病理生理学的影响。我们测量了谷胱甘肽（依赖）代谢物含量和代谢效应，包括在突变体中的活力、耗氧量、ADH1 转录本以及谷胱甘肽还原酶和α-酮戊二酸脱氢酶的活性。基于这些发现，监测了甲基乙二醛氧化蛋白，以确定 MGD1/GRP2 破坏对谷胱甘肽剥夺期间甲基乙二醛清除特性的影响。
发现仅在谷胱甘肽营养缺陷型中存在依赖 NAD（H）的甲基乙二醛氧化 Mgd1/Grp2，它可以催化甲基乙二醛和丙酮酸的还原。MGD1/GRP2 缺失突变体表现出生长缺陷、细胞周期停滞以及线粒体损伤导致的甲基乙二醛和丙酮酸积累，无论 ADH1 是否补偿。其他甲基乙二醛氧化酶被鉴定为关键的糖酵解酶，在 MGD1/GRP2 缺失突变体中活性和转录增强，而与谷胱甘肽含量无关。
M gd1/Grp2 缺乏导致甲基乙二醛和丙酮酸的同化作用失败，尽管 Adh1 进行了补偿，但仍导致谷胱甘肽依赖的氧化还原调节不良。
这是第一个报道表明多功能 Mgd 活性有助于通过糖酵解酶和 Adh1 表达清除甲基乙二醛和丙酮酸，以维持代谢稳态和氧化还原池。
