Finding enzymes in the gut metagenome

Metagenomic data help to elucidate enzymatic pathways in the human gut microbiome The human gut microbiome consists of trillions of microorganisms that colonize the colon ( 1 ). The composition of this microbiome has profound effects on human health: It not only influences normal processes, like maturation of the immune system, but it is also associated with cardiovascular, gastrointestinal, and other diseases ( 2 ). Understanding these influences requires knowledge of the biochemical interactions between the gut microbiome and humans. On page 595 of this issue, Levin et al. ( 3 ) show that combining genomic and biochemical knowledge can reveal unknown enzymatic pathways in microbiomes. Using a novel workflow, they uncover a universal pathway for metabolizing trans -4-hydroxy- l -proline, a modified amino acid that is common in dietary and human proteins.