Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Department of Biochemistry, Charitéplatz 1, D-10117 Berlin, Germany.
Lipidomix GmbH, Robert-Rössler-Straße 10, 13125 Berlin, Germany.
Biochim Biophys Acta Mol Cell Biol Lipids. 2025 Jan;1870(1):159569. doi: 10.1016/j.bbalip.2024.159569. Epub 2024 Oct 9.
Eicosanoids and related compounds are pleiotropic lipid mediators, which play a role in cell differentiation and in the pathogenesis of various diseases. The biosynthesis of these lipids has extensively been studied in highly developed mammals including humans but little is known about the formation of these mediators in more ancient Prototheria. We searched the genomes of two extant prototherian species (platypus, short-beaked echidna) for genes encoding for lipoxygenase- (ALOX) and prostaglandin synthase-isoforms (PTGS) and detected intact single copy genes for ALOX5, ALOX12, ALOX12B, ALOXE3, PTGS1 and PTGS2. Moreover, we identified two copies of ALOX15B genes (ALOX15B-1 and ALOX15B-2) but in echidna the ALOX15B-2 gene was structurally corrupted. Interestingly, in the two genomes ALOX15 genes were lacking. For functional characterization we expressed the prototherian ALOX15B isoforms and compared important enzyme characteristics of the wildtype proteins and of relevant enzyme mutants with those of human and mouse ALOX15B. Here we observed that the prototherian ALOX15B isoforms exhibit the same reaction specificity as their human ortholog. Mutagenesis of the Triad determinants did not alter the reaction specificity of the prototherian enzymes but modification of the Jisaka determinants murinized the catalytic properties. These data indicate that Prototheria exhibit an active eicosanoid metabolism. They express functional ALOX15B orthologs but lack ALOX15 genes. These observations and the previous findings that ALOX15 orthologs rarely occur in non-mammalian vertebrates such as fish and birds suggest that ALOX15 orthologs were introduced during Prototheria-Metatheria transition via an ALOX15B gene duplication and subsequent divergent enzyme evolution.
二十烷类化合物和相关化合物是多效脂质介质，在细胞分化和各种疾病的发病机制中发挥作用。这些脂质的生物合成在包括人类在内的高度发达的哺乳动物中得到了广泛研究，但对于更古老的原兽类中这些介质的形成知之甚少。我们在两种现存的原兽类物种（鸭嘴兽、短吻针鼹）的基因组中搜索编码脂氧合酶（ALOX）和前列腺素合酶同工型（PTGS）的基因，并检测到完整的单拷贝基因 ALOX5、ALOX12、ALOX12B、ALOXE3、PTGS1 和 PTGS2。此外，我们还鉴定了两个 ALOX15B 基因（ALOX15B-1 和 ALOX15B-2）的副本，但在针鼹中，ALOX15B-2 基因结构受损。有趣的是，在这两个基因组中，都缺乏 ALOX15 基因。为了进行功能表征，我们表达了原兽类 ALOX15B 同工型，并将野生型蛋白和相关酶突变体的重要酶特性与人类和小鼠 ALOX15B 的特性进行了比较。在这里，我们观察到原兽类 ALOX15B 同工型表现出与人类同源物相同的反应特异性。三联体决定因素的突变没有改变原兽类酶的反应特异性，但 Jisaka 决定因素的修饰使催化特性鼠化。这些数据表明原兽类具有活跃的类二十烷代谢。它们表达功能性 ALOX15B 同源物，但缺乏 ALOX15 基因。这些观察结果以及之前的发现表明，在鱼类和鸟类等非哺乳动物脊椎动物中，ALOX15 同源物很少出现，这表明 ALOX15 同源物是在原兽类-后兽类过渡期间通过 ALOX15B 基因复制和随后的酶进化分歧引入的。
