Aminoacyl-tRNA-Utilizing Enzymes in Natural Product Biosynthesis

Aminoacyl-tRNAs were long thought to be involved solely in ribosome-dependent protein synthesis and essential primary metabolism processes, such as targeted protein degradation and peptidoglycan synthesis. About 10 years ago, an aminoacyl-tRNA-dependent enzyme involved in the biosynthesis of the antibiotic valanimycin was discovered in a Streptomyces strain. Far from being an isolated case, this discovery has been followed by the description of an increasing number of aminoacyl-tRNA-dependent enzymes involved in secondary metabolism. This review describes the three groups of aminoacyl-tRNA-dependent enzymes involved in the synthesis of natural products. Each group is characterized by a particular chemical reaction, and its members are predicted to share a specific fold. The three groups are cyclodipeptide synthases involved in diketopiperazine synthesis, LanB-like dehydratases involved in the posttranslational modification of ribosomal peptides, and transferases from various biosynthesis pathways.