Amine-transaminases (ATAs) are enzymes that catalyze the reversible transfer of an amino group between primary amines and carbonyl compounds. They have been widely studied in the last decades for their application in stereoselective synthesis of chiral amines, which are one of the most valuable building blocks in pharmaceuticals manufacturing. Their excellent enantioselectivity, use of low-cost substrates and no need for external cofactors has turned these enzymes into a promising alternative to the chemical synthesis of chiral amines. Nevertheless, its application at industrial scale remains limited mainly because most of the available ATAs are scarcely tolerant to harsh reaction conditions such as high temperatures and presence of organic solvents. In this work, a novel (S)-ATA was discovered in a thermophilic bacterium, Albidovulum sp. SLM16, isolated from a geothermal Antarctic environmental sample, more specifically from a shoreline fumarole in Deception Island. The transaminase-coding gene was identified in the genome of the microorganism, cloned and overexpressed in Escherichia coli for biochemical characterization. The activity of the recombinant ATA was optimal at 65 °C and pH 9.5. Molecular mass estimates suggest a 75 kDa homodimeric structure. The enzyme turned out to be highly thermostable, maintaining 80% of its specific activity after 5 days of incubation at 50 °C. These results indicate that ATA_SLM16 is an excellent candidate for potential applications in biocatalytic synthesis. To the best of our knowledge, this would be the first report of the characterization of a thermostable (S)-ATA discovered by means of in vivo screening of thermophilic microorganisms.

中文翻译：

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来自南极中等嗜热细菌 Albidovulum sp. 的新型热稳定 (S)-胺-转氨酶的表征。SLM16

氨基转氨酶 (ATA) 是催化氨基在伯胺和羰基化合物之间可逆转移的酶。在过去的几十年中，它们在手性胺的立体选择性合成中的应用得到了广泛的研究，手性胺是药物制造中最有价值的组成部分之一。它们出色的对映选择性、低成本底物的使用和不需要外部辅助因子的作用使这些酶成为手性胺化学合成的有前途的替代品。然而，其在工业规模上的应用仍然受到限制，主要是因为大多数可用的 ATA 几乎不能耐受苛刻的反应条件，例如高温和有机溶剂的存在。在这项工作中，在嗜热细菌 Albidovulum sp. 中发现了一种新型 (S)-ATA。SLM16，从南极地热环境样本中分离出来，更具体地说，是从欺骗岛的海岸线喷气孔中分离出来的。在微生物的基因组中鉴定转氨酶编码基因，在大肠杆菌中进行克隆和过表达以进行生化表征。重组 ATA 的活性在 65 °C 和 pH 9.5 时最佳。分子质量估计表明具有 75 kDa 的同源二聚体结构。结果证明，该酶具有高度的热稳定性，在 50°C 下培养 5 天后仍能保持其 80% 的比活性。这些结果表明 ATA_SLM16 是生物催化合成中潜在应用的极好候选者。据我们所知，这将是通过体内筛选嗜热微生物发现的热稳定 (S)-ATA 表征的第一份报告。