The Omega class of glutathione transferases (GSTs) forms a distinct class within the cytosolic GST superfamily because most of them possess a catalytic cysteine residue. The human GST Omega 1 isoform was first characterized twenty years ago, but it took years of work to clarify the roles of the human isoforms. Concerning the kingdom of fungi, little is known about the cellular functions of Omega glutathione transferases (GSTOs), although they are widely represented in some of these organisms. In this study, we re-assess the phylogeny and the classification of GSTOs based on 240 genomes of mushroom-forming fungi (Agaricomycetes). We observe that the number of GSTOs is not only extended in the order of Polyporales but also in other orders such as Boletales. Our analysis leads to a new classification in which the fungal GSTOs are divided into two Types A and B. The catalytic residue of Type-A is either cysteine or serine, while that of Type-B is cysteine. The present study focuses on Trametes versicolor GSTO isoforms that possess a catalytic cysteine residue. Transcriptomic data show that Type-A GSTOs are constitutive enzymes while Type-B are inducible ones. The crystallographic analysis reveals substantial structural differences between the two types while they have similar biochemical profiles in the tested conditions. Additionally, these enzymes have the ability to bind antioxidant molecules such as wood polyphenols in two possible binding sites as observed from X-ray structures. The multiplication of GSTOs could allow fungal organisms to adapt more easily to new environments.

Omega 类谷胱甘肽转移酶 (GST) 在胞质 GST 超家族中形成了一个独特的类别，因为它们中的大多数都具有催化性半胱氨酸残基。人类 GST Omega 1 异构体在 20 年前首次被表征，但花了数年的时间来阐明人类异构体的作用。关于真菌界，我们对 Omega 谷胱甘肽转移酶 (GSTO) 的细胞功能知之甚少，尽管它们在其中一些生物体中广泛存在。在这项研究中，我们基于 240 个蘑菇形成真菌（蘑菇纲）的基因组重新评估了 GSTO 的系统发育和分类。我们观察到 GSTO 的数量不仅以 Polyporales 的顺序扩展，而且以其他顺序（例如 Boletales）扩展。我们的分析导致了一种新的分类，其中真菌 GSTO 分为 A 型和 B 型两种。 A 型的催化残基是半胱氨酸或丝氨酸，而 B 型的催化残基是半胱氨酸。本研究侧重于具有催化半胱氨酸残基的变色栓菌GSTO 同种型。转录组学数据显示，A 型 GSTO 是组成型酶，而 B 型是诱导型酶。晶体学分析揭示了两种类型之间的实质性结构差异，而它们在测试条件下具有相似的生化特征。此外，这些酶能够在两个可能的结合位点结合抗氧化分子，如从 X 射线结构中观察到的木材多酚。GSTO 的增殖可以使真菌生物更容易适应新环境。