Abstract
N-methylated amino acids are found in Nature in various biological compounds. N-methylation of amino acids has been shown to improve pharmacokinetic properties of peptide drugs due to conformational changes, improved proteolytic stability and/or higher lipophilicity. Due to these characteristics N-methylated amino acids received increasing interest by the pharmaceutical industry. Syntheses of N-methylated amino acids by chemical and biocatalytic approaches are known, but often show incomplete stereoselectivity, low yields or expensive co-factor regeneration. So far a one-step fermentative process from sugars has not yet been described. Here, a one-step conversion of sugars and methylamine to the N-methylated amino acid N-methyl-L-alanine was developed. A whole-cell biocatalyst was derived from a pyruvate overproducing C. glutamicum strain by heterologous expression of the N-methyl-L-amino acid dehydrogenase gene from Pseudomonas putida. As proof-of-concept, N-methyl-L-alanine titers of 31.7 g L(-1) with a yield of 0.71 g per g glucose were achieved in fed-batch cultivation. The C. glutamicum strain producing this imine reductase enzyme was engineered further to extend this green chemistry route to production of N-methyl-L-alanine from alternative feed stocks such as starch or the lignocellulosic sugars xylose and arabinose.