Interest is rising in the agrochemical and pharmaceutical industries concerning the use of enantiomerically pure amino acids. l-Amino acids are easily produced by deracemization of D,L-mixtures or by stereoinversion of d-amino acids, employing the flavoenzyme d-amino acid oxidase. On the other hand, the production of the D-enantiomers is hampered by the lack of a suitable enzyme with reversed stereoselectivity. In recent years, the enzyme l-amino acid deaminase has been proposed as an alternative to l-amino acid oxidase. l-Amino acid deaminase from Proteus myxofaciens (PmaLAAD) is a membrane-bound flavoprotein that catalyzes the deamination of l-amino acids to the corresponding α-keto acids and ammonia without producing hydrogen peroxide since the electrons are transferred from the reduced cofactor to a b-type cytochrome. For this reason, purified PmaLAAD has no significant enzymatic activity; this can be recovered by adding exogenous E. coli membranes. In order to circumvent the use of membranes, we analyzed the ability of PmaLAAD to use alternative electron acceptors, as well as detergents, to reproduce the hydrophobic environment. With phenazine methosulfate (PMS) and anionic detergents, at concentrations lower than the critical micellar concentration, higher enzymatic activity can be reached than with membranes. The effect on stability, protein conformation, oligomeric state and activity of temperature, pH, ionic strength, and detergents was also investigated. By optimizing the reaction conditions (namely, using 0.8 mM PMS and 0.1 mM SDS) the rate of l-leucine bioconversion was improved.

在农业化学和制药工业中，有关使用对映体纯氨基酸的兴趣正在上升。升氨基酸很容易通过d，L-混合物的去外消旋或通过stereoinversion产生d -氨基酸，采用黄素酶d -氨基酸氧化酶。另一方面，D-对映异构体的生产由于缺乏合适的具有相反立体选择性的酶而受到阻碍。近年来，已经提出了1-氨基酸脱氨酶作为1-氨基酸氧化酶的替代物。变形杆菌（Proteus myxofaciens）（PmaLAAD）的1-氨基酸脱氨酶是一种膜结合型黄素蛋白，可催化脱氨酶的脱氨反应。由于电子从还原的辅因子转移到b型细胞色素，所以1-氨基酸转化为相应的α-酮酸和氨而不会产生过氧化氢。因此，纯化的PmaLAAD没有明显的酶促活性。可以通过添加外源大肠杆菌来恢复膜。为了避免使用膜，我们分析了PmaLAAD使用替代电子受体和去污剂来复制疏水环境的能力。使用浓度低于临界胶束浓度的甲基硫酸吩嗪硫酸盐（PMS）和阴离子去污剂，可以获得比膜更高的酶促活性。还研究了对稳定性，蛋白质构象，低聚状态和温度，pH，离子强度和去污剂活性的影响。通过优化反应条件（即，使用0.8mM PMS和0.1mM SDS），提高了1-亮氨酸生物转化率。