the enzymatic and metabolic capabilities of early life早期生活的酶和代谢功能.pdf

The Enzymatic and Metabolic Capabilities of Early Life 1 2,3 3,4 Aaron David Goldman *, John A. Baross , Ram Samudrala 1 Department of Ecology and Evolutionary Biology, Princeton, New Jersey, United States of America, 2 School of Oceanography, University of Washington, Seattle, Washington, United States of America, 3 Center for Astrobiology and Early Evolution, University of Washington, Seattle, Washington, United States of America, 4 Department of Microbiology, University of Washington, Seattle, Washington, United States of America Abstract We introduce the concept of metaconsensus and employ it to make high confidence predictions of early enzyme functions and the metabolic properties that they may have produced. Several independent studies have used comparative bioinformatics methods to identify taxonomically broad features of genomic sequence data, protein structure data, and metabolic pathway data in order to predict physiological features that were present in early, ancestral life forms. But all such methods carry with them some level of technical bias. Here, we cross-reference the results of these previous studies to determine enzyme functions predicted to be ancient by multiple methods. We survey modern metabolic pathways to identify those that maintain the highest frequency of metaconsensus enzymes. Using the full set of modern reactions catalyzed by these metaconsensus enzyme functions, we reconstruct a representative metabolic network that may reflect the core metabolism of early life forms. Our results show that ten enzyme functions, four hydrolases, three transferases, one oxidoreductase, one lyase, and one ligase, are determined