Identification, Heterologous Expression and Characterization of a Transaminase from Rhizobium sp.

In present study, we have mined a transaminase (TA) from Rhizobium sp. from the pool of fully sequenced genomes by using an ω-TA sequence from Vibrio fluvialis JS17 as a template in a BLASTP search. The protein sequence of the TA from Rhizobium sp. exhibits 53% sequence identity to that from V. fluvialis. The TA with S-selectivity showed close evolutionary relationship with a pyruvate transaminase from Alcaligenes denitrificans Y2k-2 and an S-selective aminotransferase from Sphaerobacter thermophilus. The gene of the ω-TA was inserted into pET-28a and functionally expressed in E. coli BL21. Results showed that the recombinant ω-TA has a specific activity of 7.46 U/mg at pH 8.0, 30 ℃. The substrate specificity test found the ω-TA presented significant reactivity toward aromatic amino donors and amino acceptors containing aldehydes. More importantly, the ω-TA also exhibited a good affinity towards some cyclic substrates. The homology model of the ω-TA was built by Discovery Studio and docking was performed to describe the relative activity towards some substrates.