School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA.
School of Chemistry and Biochemistry, and Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA.
Mol Biol Evol. 2018 Sep 1;35(9):2185-2197. doi: 10.1093/molbev/msy120.
Isoprenoids and their derivatives represent the largest group of organic compounds in nature and are distributed universally in the three domains of life. Isoprenoids are biosynthesized from isoprenyl diphosphate units, generated by two distinctive biosynthetic pathways: mevalonate pathway and methylerthritol 4-phosphate pathway. Archaea and eukaryotes exclusively have the former pathway, while most bacteria have the latter. Some bacteria, however, are known to possess the mevalonate pathway genes. Understanding the evolutionary history of these two isoprenoid biosynthesis pathways in each domain of life is critical since isoprenoids are so interweaved in the architecture of life that they would have had indispensable roles in the early evolution of life. Our study provides a detailed phylogenetic analysis of enzymes involved in the mevalonate pathway and sheds new light on its evolutionary history. The results suggest that a potential mevalonate pathway is present in the recently discovered superphylum Candidate Phyla Radiation (CPR), and further suggest a strong evolutionary relationship exists between archaea and CPR. Interestingly, CPR harbors the characteristics of both the bacterial-type and archaeal-type mevalonate pathways and may retain signatures regarding the ancestral isoprenoid biosynthesis pathway in the last universal common ancestor. Our study supports the ancient origin of the mevalonate pathway in the three domains of life as previously inferred, but concludes that the evolution of the mevalonate pathway was more complex.
类异戊二烯及其衍生物是自然界中最大的有机化合物群体，普遍存在于生命的三个领域。类异戊二烯由异戊烯二磷酸单元生物合成，这些单元由两种独特的生物合成途径产生：甲羟戊酸途径和甲基赤藓醇 4-磷酸途径。古菌和真核生物仅具有前者，而大多数细菌具有后者。然而，有些细菌被认为具有甲羟戊酸途径基因。了解这两种类异戊二烯生物合成途径在生命各个领域的进化历史至关重要，因为类异戊二烯在生命结构中如此交织，它们在生命的早期进化中具有不可或缺的作用。我们的研究提供了参与甲羟戊酸途径的酶的详细系统发育分析，并为其进化历史提供了新的见解。结果表明，最近发现的候选门辐射（CPR）超门中存在潜在的甲羟戊酸途径，并且古菌和 CPR 之间存在强烈的进化关系。有趣的是，CPR 具有细菌型和古菌型甲羟戊酸途径的特征，并且可能在最后的普遍共同祖先中保留有关祖先类异戊二烯生物合成途径的特征。我们的研究支持甲羟戊酸途径在生命的三个领域中的古老起源，如先前推断的那样，但得出的结论是，甲羟戊酸途径的进化更加复杂。
