A transaminase from Halomonas elongata and four mutants generated by an in silico-based design were recombinantly produced in E. coli, purified and applied to the amination of mono-substituted aromatic carbonyl-derivatives. While benzaldehyde derivatives were excellent substrates, only NO₂-acetophenones were transformed into the (S)-amine with a high enantioselectivity. The different behaviour of wild-type and mutated transaminases was assessed by in silico substrate binding mode studies.