Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
Chembiochem. 2018 Jul 4;19(13):1452-1460. doi: 10.1002/cbic.201800157. Epub 2018 Jun 8.
Carboxylic acid reductases (CARs) catalyze the reduction of a broad range of carboxylic acids into aldehydes, which can serve as common biosynthetic precursors to many industrial chemicals. This work presents the systematic biochemical characterization of five carboxylic acid reductases from different microorganisms, including two known and three new ones, by using a panel of short-chain dicarboxylic acids and hydroxy acids, which are common cellular metabolites. All enzymes displayed broad substrate specificities. Higher catalytic efficiencies were observed when the carbon chain length, either of the dicarboxylates or of the terminal hydroxy acids, was increased from C to C . In addition, when substrates of the same carbon chain length are compared, carboxylic acid reductases favor hydroxy acids over dicarboxylates as their substrates. Whole-cell bioconversions of eleven carboxylic acid substrates into the corresponding alcohols were investigated by coupling the CAR activity with that of an aldehyde reductase in Escherichia coli hosts. Alcohol products were obtained in yields ranging from 0.5 % to 71 %. The de novo stereospecific biosynthesis of propane-1,2-diol enantiomer was successfully demonstrated with use of CARs as the key pathway enzymes. E. coli strains accumulated 7.0 mm (R)-1,2-PDO (1.0 % yield) or 9.6 mm (S)-1,2-PDO (1.4 % yield) from glucose. This study consolidates carboxylic acid reductases as promising enzymes for sustainable synthesis of industrial chemicals.
羧酸还原酶（CARs）能够催化多种羧酸还原为醛，而醛可以作为许多工业化学品的常见生物合成前体。本研究通过使用一系列短链二羧酸和羟基酸（常见的细胞代谢物），对来自不同微生物的五种羧酸还原酶（两种已知和三种新的）进行了系统的生化特性分析。所有酶都表现出广泛的底物特异性。当二羧酸或末端羟基酸的碳链长度从 C 增加到 C 时，观察到更高的催化效率。此外，当比较具有相同碳链长度的底物时，羧酸还原酶更倾向于将羟基酸作为其底物，而不是二羧酸。通过将 CAR 活性与大肠杆菌中醛还原酶的活性偶联，研究了 11 种羧酸底物转化为相应醇的全细胞生物转化。醇产物的产率范围为 0.5%至 71%。利用 CARs 作为关键途径酶，成功地证明了丙烷-1,2-二醇对映体的从头立体特异性生物合成。大肠杆菌菌株从葡萄糖中积累了 7.0mm（R）-1,2-PDO（1.0%产率）或 9.6mm（S）-1,2-PDO（1.4%产率）。本研究证实羧酸还原酶是可持续合成工业化学品的有前途的酶。
