Recently, a putative alcohol dehydrogenase 3, termed EhADH3B of the Entamoeba histolytica isolate HM-1:IMSS was identified, which is expressed at higher levels in non-pathogenic than in pathogenic amoebae and whose overexpression reduces the virulence of pathogenic amoebae. In an in silico analysis performed in this study, we assigned EhADH3B to a four-member ADH3 family, with ehadh3b present as a duplicate (ehadh3b^a/ehadh3b^b). In long-term laboratory cultures a mutation was identified at position 496 of ehadh3b^a, which codes for a stop codon, which was not the case for amoebae isolated from human stool samples. When using transfectants that overexpress or silence ehadh3b^b, we found no or little effect on growth, size, erythrophagocytosis, motility, hemolytic or cysteine peptidase activity. Biochemical characterization of the recombinant EhADH3B^b revealed that this protein forms a dimer containing Ni²⁺ or Zn²⁺ as a co-factor and that the enzyme converts acetaldehyde and formaldehyde in the presence of NADPH. A catalytic activity based on alcohols as substrates was not detected. Based on the results, we postulate that EhADH3B^b can reduce free acetaldehyde released by hydrolysis from bifunctional acetaldehyde/alcohol dehydrogenase-bound thiohemiacetal and that it is involved in detoxification of toxic aldehydes produced by the host or the gut microbiota.

中文翻译：

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来自解脂Entamoeba histolytica的酒精脱氢酶3（ADH3）参与有毒醛的解毒

最近，鉴定出一种推定的醇脱氢酶3，称为解脂变形杆菌Entamoeba组织溶菌HM-1：IMSS的EhADH3B ，其在非致病性表达水平高于致病性变形杆菌，并且其过表达降低了致病性变形杆菌的毒力。在这项研究中进行的计算机分析中，我们将EhADH3B分配给一个四成员ADH3家族，其中ehadh3b是重复的（ehadh3b ^a / ehadh3b ^b）。在长期的实验室培养中，在ehadh3b ^a的496位发现^了一个突变，其编码终止密码子，而从人类粪便样品中分离出的变形虫则不是这种情况。当使用过表达或沉默ehadh3b ^b的转染子时，我们发现对生长，大小，红细胞吞噬作用，运动性，溶血或半胱氨酸肽酶活性几乎没有影响。重组EhADH3B ^b的生化特性表明，该蛋白质形成了以Ni ²⁺或Zn ²⁺为辅因子的二聚体，并且该酶在NADPH存在下转化了乙醛和甲醛。未检测到基于醇作为底物的催化活性。根据结果​​，我们假设EhADH3B ^b 可以减少由双功能乙醛/乙醇脱氢酶结合的硫半缩醛水解释放的游离乙醛，并且可以参与宿主或肠道菌群产生的有毒醛的解毒。