Today the vast amount of newly published genomic data is generated by metagenomic projects. The annotation of these sequences of organisms, whose existence was not even known before their DNA was extracted from environmental samples, has led to the identification of thousands of new protein families with no detectable homology to any proteins in sequenced and cultivable organisms. While these protein families now make up a major part of the protein universe, we do not know anything about their functions or biocatalytic activity. In this grant application, we propose to lay the groundwork for studying the function of this vast set of proteins and exploit their biocatalytic potential. However, many of the techniques traditionally used to elucidate protein function, such as genetics and “omics”-technologies are not applicable, because the organisms in which these proteins exist are as of yet unknown. Therefore we plan to:1. Computationally analyze the newly discovered protein families to identify one paradigmatic member of every novel family.2. Create an expression-plasmid library of those paradigmatic representatives by de novo gene-synthesis.3. Use this library, combined with the power of Escherichia coli genetics, for specific complementation studies and biochemical assays to assign functions to novel protein families.This combination of synthetic biology and metagenomics will provide the starting point for a novel systematic approach to harness the biocatalytic potential and to understand the function of an unknown sector of biology that has only very recently been discovered.