Structure-guided engineering of Pseudomonas dacunhael-aspartate β-decarboxylase for l-homophenylalanine synthesis

Structure-guided engineering of branched-chain α-keto acid decarboxylase for improved 1,2,4-butanetriol production by in vitro synthetic enzymatic biosystem

Efficient synthetic routes for biomanufacturing chemicals often require the overcoming of pathway bottlenecks by tailoring enzymes to improve the catalytic efficiency or even implement non-native activities. 1,2,4-butanetriol (BTO), a valuable commodity chemical, is currently biosynthesized from D-xylose via a four-enzyme reaction cascade, with the ThDP-dependent α-keto acid decarboxylase (KdcA) identified as the potential bottleneck. Here, to further enhance the catalytic activity of KdcA toward the non-native substrate α-keto-3-deoxy-xylonate (KDX), in silico screening and structure-guided evolution were performed. The best mutants, S286L/G402P and V461K, exhibited a 1.8- and 2.5-fold higher enzymatic activity in the conversion of KDX to 3,4-dihydroxybutanal when compared to KdcA, respectively. MD simulations revealed that the two sets of mutations reshaped the substrate binding pocket, thereby increasing the binding affinity for KDX and promoting interactions between KDX and cofactor ThDP. Then, when the V461K mutant instead of wild type KdcA was integrated into the enzyme cascade, a 1.9-fold increase in BTO titer was observed. After optimization of the reaction conditions, the enzyme cocktail contained V461K converted 60 g/L D-xylose to 22.1 g/L BTO with a yield of 52.1 %. This work illustrated that protein engineering is a powerful tool for modifying the output of metabolic pathway.

Green light enhanced the photostability and catalytic performance of fatty acid photodecarboxylase

Green light was documented to improve the photostability of fatty acid photodecarboxylase from Chlorella variabilis (CvFAP). Compared to blue light, green light increased the pentadecane yield by 27.6% and improved the residual activity of CvFAP to 5.9-fold after the preillumination. Kinetics and thermodynamics indicated that blue light facilitated a high CvFAP activity.

Carving the Active Site of CYP153A7 Monooxygenase for Improving Terminal Hydroxylation of Medium-Chain Fatty Acids

The P450-mediated terminal hydroxylation of non-activated C-H bonds is a chemically challenging reaction. CYP153A7 monooxygenase discovered in Sphingomonas sp. HXN200 belongs to the CYP153A subfamily and shows a pronounced terminal selectivity. Herein, we report the significantly improved terminal hydroxylation activity of CYP153A7 by redesign of the substrate binding pocket based on molecular docking of CYP153A7-C 8:0 and sequence alignments. Some of the resultant single mutants were advantageous over the wild-type enzyme with higher reaction rates, achieving a complete conversion of n- octanoic acid (C 8:0. 1 mM) in a shorter period. Especially, a single-mutation variant, D258E, showed 3.8-fold higher catalytic efficiency than the wild type toward the terminal hydroxylation of medium-chain fatty acid C 8:0 into the high value-added product 8-hydroxyoctanoic acid.