Means and methods for synthesizing precursors of y-aminobutyric acid (gaba) analogs

The invention relates to the fields of drug development and biocatalysis, more specifically to a biocatalytic route for asymmetric synthesis of precursors of y-aminobutyric acid (GABA) analogs. Provided is an isolated mutant 4-oxalocrototonate tautomerase (4-OT) enzyme comprising the following mutations (i) leucine at position 8 substituted with a tyrosine (L8Y) or a phenylalanine (L8F); (ii) methionine at position 45 substituted with a tyrosine (M45Y); and (iii) phenylalanine at position 50 substituted with an alanine (F50A), wherein the positions are numbered according to the amino acid sequence of 4-OT of Pseudomonas putida. Also provided is a method for the synthesis of a precursor for the pharmaceutically relevant enantiomer of a GABA analog, comprising (i) providing a y-nitroaldehyde using the 4-OT mutant enzyme, followed by (ii) subjecting the thus obtained y-nitroaldehyde to an enzymatic oxidation reaction catalyzed by an aldehyde dehydrogenase (EC 1.2.1.3)

Enantioselective Synthesis of Pharmaceutically Active γ-Aminobutyric Acids Using a Tailor-Made Artificial Michaelase in One-Pot Cascade Reactions

Chiral γ-aminobutyric acid (GABA) analogues represent abundantly prescribed drugs, which are broadly applied as anticonvulsants, as antidepressants, and for the treatment of neuropathic pain. Here we report a one-pot two-step biocatalytic cascade route for synthesis of the pharmaceutically relevant enantiomers of γ-nitrobutyric acids, starting from simple precursors (acetaldehyde and nitroalkenes), using a tailor-made highly enantioselective artificial “Michaelase” (4-oxalocrotonate tautomerase mutant L8Y/M45Y/F50A), an aldehyde dehydrogenase with a broad non-natural substrate scope, and a cofactor recycling system. We also report a three-step chemoenzymatic cascade route for the efficient chemical reduction of enzymatically prepared γ-nitrobutyric acids into GABA analogues in one pot, achieving high enantiopurity (e.r. up to 99:1) and high overall yields (up to 70%). This chemoenzymatic methodology offers a step-economic alternative route to important pharmaceutically active GABA analogues, and highlights the exciting opportunities available for combining chemocatalysts, natural enzymes, and designed artificial biocatalysts in multistep syntheses

Using mutability landscapes of a promiscuous tautomerase to guide the engineering of enantioselective Michaelases

The Michael-type addition reaction is widely used in organic synthesis for carbon-carbon bond formation. However, biocatalytic methodologies for this type of reaction are scarce, which is related to the fact that enzymes naturally catalysing carbon-carbon bond-forming Michael-type additions are rare. A promising template to develop new biocatalysts for carbon-carbon bond formation is the enzyme 4-oxalocrotonate tautomerase, which exhibits promiscuous Michael-type addition activity. Here we present mutability landscapes for the expression, tautomerase and Michael-type addition activities, and enantioselectivity of 4-oxalocrotonate tautomerase. These maps of neutral, beneficial and detrimental amino acids for each residue position and enzyme property provide detailed insight into sequence-function relationships. This offers exciting opportunities for enzyme engineering, which is illustrated by the redesign of 4-oxalocrotonate tautomerase into two enantiocomplementary 'Michaelases'. These 'Michaelases' catalyse the asymmetric addition of acetaldehyde to various nitroolefins, providing access to both enantiomers of γ-nitroaldehydes, which are important precursors for pharmaceutically active γ-aminobutyric acid derivatives

Mutability-landscape guided enzyme engineering: Improving the promiscuous C-C bond-forming activities of 4-oxalocrotonate tautomerase

Enzymes do not only play a crucial role in nature, they are also increasingly used as biocatalysts for the production of complex molecules such as pharmaceuticals. However, some of the reactions that are widely used in organic synthesis have not been observed in biological systems. Hence, there is no biocatalytic alternative available for those important reactions. One way of generating enzymes for these unnatural reactions is by exploiting the catalytic promiscuity of existing enzymes. Jan Ytzen van der Meer has improved two promiscuous C-C bond-forming activities of the enzyme 4-oxalocrotonate tautomerase (4-OT). For improving the promiscuous Michael-type addition activity of 4-OT, he first determined the effects of nearly all possible single amino acid substitutions on both activity and enantioselectivity. In the resulting mutability landscapes, all positive, neutral and detrimental effects of these mutations are displayed. Guided by these mutability landscapes of 4-OT, he then generated a set of highly active and enantiocomplementary ‘Michaelases’. These enantioselective enzymes can be used for the convenient synthesis of both enantiomers of γ-nitroaldehydes, which are important precursors for pharmaceutically active GABA derivatives. The second promiscuous activity of 4-OT that was improved was the aldolase activity. Based on a similar approach, three residue positions were identified in 4-OT at which mutations led to a marked improvement of the promiscuous aldolase activity. Combinations of these mutations further improved this aldolase activity of 4-OT, allowing the enzymatic self- and cross-coupling of various aldehydes. Taken together, the work described in the thesis of Jan Ytzen van der Meer provides insights in the generation and application of mutability landscapes for efficient enzyme engineering and yielded comprehensive mutational data, which might be used as a unique training set to improve computational tools for enzyme engineering

The isoprenoid-precursor dependence of Plasmodium spp.

Due to the increase in resistance of Plasmodium spp. against available antimalarials, there is a need for new, effective and innovative drugs. The non-mevalonate pathway for the biosynthesis of the universal isoprenoid precursors, which is absent in humans, is suggested as an attractive source of targets for such drugs with a novel mode of action. The biological importance of this pathway to Plasmodium spp. is proven by the efficacy of the clinical candidate fosmidomycin, which inhibits the biosynthesis of isoprenoid precursors; it is, however, less clear which isoprenoid end products are essential for parasite survival. In this Highlight, we identify protein prenylation, isoprene-containing quinone production, N-linked glycosylation as well as carotenoid and vitamin-E biosynthesis as probably essential isoprenoid-dependent physiological processes in Plasmodium. Inhibition of any of these processes blocks parasite development. Furthermore, both protein prenylation of SNARE proteins and a protein tyrosine phosphatase as well as tRNA prenylation have been identified as isoprene-dependent processes for which the physiological role in Plasmodium remains unclear. Therefore, the biosynthetic route to the isoprenoid precursors presents attractive drug targets for the development of antimalarials with novel modes of action.