Biocatalysis research has significantly developed these last decades due to its great potential to strengthen the chemical and pharmaceutical industries through the use of enzymes, which can (1) lead to sustainable and energy-efficient production methods, and (2) enable the production of high-value fine chemicals and pharmaceutical compounds that would otherwise be inaccessible. Although some enzymes do not require any additional chemicals for their catalytic activity other than their amino acid residues, many require a complementary component called cofactor.
Therefore, to study or use all naturally occurring enzymes, it is necessary to have affordable access to these cofactors. Although the use of inorganic ions seems straightforward, the price of these coenzymes can be prohibitive: 1600 €/g, 30 000 €/g or 1000 €/g for Coenzyme A (CoA), its disulfide (CoAS2) and S-adenosylmethionine (SAM) respectively.
SAM is a central metabolite and cofactor in living organisms and is of particular interest for applications in medicine as well as biocatalysis. Despite its important role and multiple applications in clinical treatments, few studies have been devoted to optimizing the synthesis and purification of SAM in vitro. In this study, we present the expression of a recombinant methionine adenosyltransferase (MAT) enzyme and its implementation in the in vitro enzymatic synthesis of SAM, followed by the optimization of the reaction by experimental design. Simultaneous absorption/desorption of the product on resin in situ was also developed. The optimal biocatalytic reaction conditions were determined and a productivity of 5 g/L was achieved allowing the increase of SAM production by 26% compared to literature values. The use of an in-situ resin allowed both a combined reduction of product inhibition and simpler purification of SAM. By screening different solvents and processing conditions, we provide proof of concept of the specific adsorption/desorption and elimination of inhibition of SAM on specific resins. Overall, this work represents a significant improvement in the in vitro enzymatic synthesis of SAM, combining easier purification of the compound with the addition of an in-situ resin. This paves the way for larger-scale, sustainable, and cost-effective production of this coenzyme.

Coline Gebeau

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