Characterisation of a novel w-transaminase from a Triassic salt mine metagenome

Chiral amines are valuable building blocks for the pharmaceutical industry, and are increasingly synthesized by transaminase-mediated (TAm) synthesis. Currently available TAms, primarily isolated from the genomes of cultured mesophilic bacteria, often suffer from a number of drawbacks, including poor substrate range and an inability to tolerate the harsh conditions often demanded by industrial processes.
These characteristics have, in part, driven the search for novel biocatalysts from both metagenomic sources and extreme environments. Herein, we report the isolation and characterization of an u-TAm from a metagenome of a Triassic salt mine in Kilroot, N. Ireland, an extremely hypersaline environment formed circa 220e250 mya. The gene sequence was identified based on homology with existing bacterial TAms, synthesized within a pET28a(þ) plasmid and expressed in E. coli BL21 DE3 cells.
This study does however reinforce the viability of mining metagenomic datasets as a means of discovering novel and functional biocatalysts, and adds to a currently scant list of such examples in the field of TAms.