Oligomerization engineering of the fluorinase enzyme leads to an active trimer that supports synthesis of fluorometabolites in vitro

Synthetic metabolism for in vitro acetone biosynthesis driven by ATP regeneration

In vitro ketone production continues to be a challenge due to the biochemical features of the enzymes involved-even when some of them have been extensively characterized (e.g. thiolase from Clostridium acetobutylicum), the assembly of synthetic enzyme cascades still face significant limitations (including issues with protein aggregation and multimerization). Here, we designed and assembled a self-sustaining enzyme cascade with acetone yields close to the theoretical maximum using acetate as the only carbon input. The efficiency of this system was further boosted by coupling the enzymatic sequence to a two-step ATP-regeneration system that enables continuous, cost-effective acetone biosynthesis. Furthermore, simple methods were implemented for purifying the enzymes necessary for this synthetic metabolism, including a first-case example on the isolation of a heterotetrameric acetate:coenzyme A transferase by affinity chromatography.

Biocatalytic synthesis of 2-fluoro-3-hydroxypropionic acid

Fluorine has become an important element for the design of synthetic molecules for use in medicine, agriculture, and materials. The introduction of fluorine atoms into organic compound molecules can often give these compounds new functions and make them have better performance. Despite the many advantages provided by fluorine for tuning key molecular properties, it is rarely found in natural metabolism. We seek to expand the molecular space available for discovery through the development of new biosynthetic strategies that cross synthetic with natural compounds. Towards this goal, 2-fluoro-3-hydroxypropionic acid (2-F-3-HP) was first synthesized using E. coli coexpressing methylmalonyl CoA synthase (MatBrp), methylmalonyl CoA reductase (MCR) and malonate transmembrane protein (MadLM). The concentration of 2-F-3-HP reached 50.0 mg/L by whole-cell transformation after 24 h. 2-F-3-HP can be used as the substrate to synthesize other fluorides, such as poly (2-fluoro-3-hydroxypropionic acid) (FP3HP). Being entirely biocatalytic, our procedure provides considerable advantages in terms of environmental and safety impacts over reported chemical methods.

Identification of Two Novel Fluorinases From Amycolatopsis sp. CA-128772 and Methanosaeta sp. PtaU1.Bin055 and a Mutant With Improved Catalytic Efficiency With Native Substrate

Fluoride plays an important role in the fields of materials and medicine. Compared with chemical synthesis, fluorinases are natural catalysts with more application potential, which provide a green and effective way to obtain organofluorine. However, the application of fluorinases is limited by certain factors, such as the limited number of enzymes and their low activity. In this work, two new fluorinases from Amycolatopsis sp. CA-128772 and Methanosaeta sp. PtaU1.Bin055 were identified by gene mining and named Fam and Fme, respectively. The activities of these two enzymes were reported for the first time, and Fme showed good thermal stability, which was different from the reported fluorinases. In addition, the activity toward natural substrate of Fam was improved by site-directed mutagenesis, the catalytic efficiency (k_cat/K_m) of the best mutant containing two amino acid substitutions (T72A and S164G) toward the substrate S-adenosyl-L-methionine was improved by 2.2-fold compared to the wild-type. Structural modeling analysis revealed that the main reason for the increased enzyme activity might be the formation of a new substrate channel. Experimental evidence suggests that the substrate channel may indeed play a key role in regulating the function of the fluorinases.

A Nonconventional Archaeal Fluorinase Identified by In Silico Mining for Enhanced Fluorine Biocatalysis

Fluorinases, the only enzymes known to catalyze the transfer of fluorine to an organic molecule, are essential catalysts for the biological synthesis of valuable organofluorines. However, the few fluorinases identified so far have low turnover rates that hamper biotechnological applications. Here, we isolated and characterized putative fluorinases retrieved from systematic in silico mining and identified a nonconventional archaeal enzyme from Methanosaeta sp. that mediates the fastest S_N2 fluorination rate reported to date. Furthermore, we demonstrate enhanced production of fluoronucleotides in vivo in a bacterial host engineered with this archaeal fluorinase, paving the way toward synthetic metabolism for efficient biohalogenation.