Biocatalytic Reductive Amination by Native Amine Dehydrogenases to Access Short Chiral Alkyl Amines and Amino Alcohols

Abstract

Small optically active molecules, and more particularly short-chain chiral amines, are key compounds in the chemical industry and precursors of various pharmaceuticals. Their chemo-biocatalytic production on a commercial scale is already established, mainly through lipase-catalyzed resolutions leading to ChiPros™ products among others. Nevertheless, their biocatalytic synthesis remains challenging for very short-chain C4 to C5 amines due to low enantiomeric excess. To complement the possibilities recently offered by transaminases, this work describes alternative biocatalytic access using amine dehydrogenases (AmDHs). Without any protein engineering, some of the already described wild-type AmDHs (CfusAmDH, MsmeAmDH, MicroAmDH, and MATOUAmDH2) were shown to be efficient for the synthesis of hydroxylated or unfunctionalized small 2-aminoalkanes. Conversions up to 97.1% were reached at 50 mM, and moderate to high enantioselectivities were obtained, especially for (S)-1-methoxypropan-2-amine (98.1%), (S)-3-aminobutan-1-ol (99.5%), (3S)-3-aminobutan-2-ol (99.4%), and the small (S)-butan-2-amine (93.6%) with MsmeAmDH. Semi-preparative scale-up experiments were successfully performed at 150 mM substrate concentrations for the synthesis of (S)-butan-2-amine and (S)-1-methoxypropan-2-amine, the latter known as “(S)-MOIPA”. Modeling studies provided some preliminary results explaining the basis for the challenging discrimination between similarly sized substituents in the active sites of these enzymes.

Structure and Mutation of the Native Amine Dehydrogenase MATOUAmDH2

“…The adenine ring of the cofactor stacks against N42 in MATOUAmDH2, but H37 in Cfus AmDH, which also provides coordination to the phosphate (Figure 4B). The overall effect in MATOUAmDH2 is to restrict the movement of the phosphate with more binding interactions and possibly explaining the stricter specificity of MATOUAmDH2 for the phosphorylated cofactor over NADH (71: 1) described previously [30] compared to Cfus AmDH, which displays a preference of 2.67 : 1 in catalytic efficiency for NADPH over NADH [29] …”

“…The acquisition of the MATOUAmDH2 structure in complex with cyclohexylamine permitted us to model substrates into the active site in order to rationalize the observed stereoselectivity of the enzyme. For example, MATOUAmDH2 was shown to catalyze the amination of 1‐methoxypropan‐2‐one 15 to ( S )‐1‐methoxypropan‐2‐amine 17 (MOIPA) (Scheme 2), an important chiral element of herbicide molecules including ( S )‐metolachlor and ( S )‐dimethenamid, [33] with 90 % e.e [30] …”

“…Relative activities of 6 % and 16 % for cyclohexanone with ethylamine and methylamine respectively ( vs cyclohexanone with ammonia) were also reported, hinting at a potential for the synthesis of secondary amines by MATOUAmDH2. Further studies established that MATOUAmDH2 also catalyzed the enantioselective production of ( S )‐short alkylamine and alkylaminoalcohols from suitable precursors including 2‐pentanone 13 , which was converted to (2 S )‐2‐pentanamine 14 with 27 % conversion and 99 % e.e [30] . The broader and distinctive substrate specificity of MATOUAmDH2 identifies it as an interesting candidate for in vitro evolution strategies targeted at improving or altering its activity, selectivity and process suitability.…”

Religious‐based negative attitudes towards LGBTQ people among healthcare, social care and social work students and professionals: A review of the international literature

“…Carbonyl substrates transformed to amines by MATOUAmDH2 with the addition of NH 3 and NADPH. [29,30] ChemBioChem…”

“…Further studies established that MATOUAmDH2 also catalyzed the enantioselective production of (S)-short alkylamine and alkylaminoalcohols from suitable precursors including 2-pentanone 13, which was converted to (2S)-2-pentanamine 14 with 27 % conversion and 99 % e.e. [30] The broader and distinctive substrate specificity of MATOUAmDH2 identifies it as an interesting candidate for in vitro evolution strategies targeted at improving or altering its activity, selectivity and process suitability. In this report we present a structural and mutational analysis of MATOUAmDH2, in the interests of providing a robust platform for rational engineering of this nat-AmDH.…”