Enantiomerically pure amino acids are of increasing interest for the fine chemical, agrochemicals and pharmaceutical industries. During past years l-amino acids have been produced from deracemization of dl-solution employing the stereoselective flavoenzyme d-amino acid oxidase. On the other hand, the isolation of corresponding d-isomer was hampered by the scarce availability of a suitable l-amino acid oxidase activity. On this side, l-amino acid deaminase (LAAD), only present in the Proteus bacteria, represents a suitable alternative. This FAD-containing enzyme catalyzes the deamination of l-amino acids to the corresponding α-keto acids and ammonia, with no hydrogen peroxide production (a potentially dangerous oxidizing species) since the electrons of the reduced cofactor are transferred to a membrane-bound cytochrome. Very recently the structure of LAAD has been solved: in addition to a FAD-binding domain and to a substrate-binding domain, it also possesses an N-terminal putative transmembrane α-helix (residues 8–27, not present in the crystallized protein variant) and a small α + β subdomain (50–67 amino acids long, named “insertion module”) strictly interconnected to the substrate binding domain. Structural comparison showed that LAAD resembles the structure of several soluble amino acid oxidases, such as l-proline dehydrogenase, glycine oxidase or sarcosine oxidase, while only a limited structural similarity with d- or l-amino acid oxidase is apparent. In this review, we present an overview of the structural and biochemical properties of known LAADs and describe the advances that have been made in their biotechnological application also taking advantage from improved variants generated by protein engineering studies.

对映体纯氨基酸对精细化工，农用化学品和制药工业越来越感兴趣。在过去的几年中升-氨基酸已经从去外消旋产生DL采用立体黄素酶-溶液d -氨基酸氧化酶。另一方面，由于缺乏合适的1-氨基酸氧化酶活性，阻碍了相应d-异构体的分离。在这一方面，仅存在于变形杆菌中的1-氨基酸脱氨酶（LAAD）代表了合适的替代方案。这种含FAD的酶催化I的脱氨基-氨基酸还原为相应的α-酮酸和氨，不会产生过氧化氢（潜在危险的氧化物质），因为还原型辅因子的电子转移到了与膜结合的细胞色素上。最近，LAAD的结构已得到解决：除了FAD结合结构域和底物结合结构域外，它还具有N端假定的跨膜α-螺旋（残基8–27，不存在于结晶蛋白中）变体）和一个小的α+β子结构域（长50-67个氨基酸，称为“插入模块”）与底物结合域严格互连。结构比较显示，LAAD类似的几个可溶性氨基酸氧化酶，如结构升-脯氨酸脱氢酶，甘氨酸氧化酶或肌氨酸氧化酶，而与d-或l-氨基酸氧化酶的结构相似性有限。在这篇综述中，我们概述了已知LAADs的结构和生化特性，并描述了其生物技术应用方面的进展，这些进展还利用了蛋白质工程研究产生的改良变体。