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1000
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Abstract/Summary
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Enantioselective transamination of amino acids is a great challenge in biotechnology as suitable enzymes with wide substrate spectrum are rare. Here, we present a new transaminase from Variovorax boronicumulans (VboTA, Variovorax boronicumulans ?-transaminase) which is specific for ?-amino acids.The amino acid sequence of VboTA is similar to an ?-transaminase from Variovorax paradoxus, for which a crystal-structure is available. This similarity is allowing us to classify VboTA as a fold type 1 ?-transaminase (?-TA). Although both enzymes have a high sequence similarity (86% identities, 92% positives), there are differences in the active center, which allow VboTA to accept a broader substrate spectrum. Both enzymes have also a different temperature stability and temperature optimum.VboTA deaminates the D-form of aromatic ?-amino acids, such as ?-homophenylalanine and ?-phenylalanine as well as aliphatic ?-amino acids, such as ?-homoalanine and ?-leucine. The optimal reaction conditions turned out to be 32 °C and pH 9. Kinetic resolution lead to high enantiomeric excess of 86.6% to >99.9%, depending on the amino donor/acceptor pair. In contrast to many other ?-TAs, VboTA has a broad substrate spectrum and uses both aromatic or aliphatic amino acids. With ?-amino acids as substrates, VboTA showed no activity at all.
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