PhD ceremony Mr. H. Raj: Engineering and biocatalytic applications of methylaspartate ammonia lyase. Asymmetric synthesis of aspartic acid derivatives

PhD ceremony: Mr. H. Raj, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Engineering and biocatalytic applications of methylaspartate ammonia lyase. Asymmetric synthesis of aspartic acid derivatives

Promotor(s): prof. G.J. Poelarends, prof. W.J. Quax

Faculty: Mathematics and Natural Sciences

Hans Raj has successfully engineered the enzyme called Methylaspartate Ammonia Lyase (MAL) and also demonstrated that the engineered mutants of MAL can be utilized for the production of non-natural amino acids. This newly developed biocatalytic methodology provides exciting opportunities for clean and environmentally friendly synthesis of a large variety of substituted aspartic acids, which are valuable as tools for neurobiological research and as chiral building blocks for pharma- and neutraceuticals (artificial sweeteners).

Amino acids are important substances for biological research and interesting building blocks for the production of low-calorie sweeteners and medicines. The synthesis of amino acids in optically pure form remains a difficult and laborious task with classical chemistry. An important and competitive alternative is the use of enzymes to synthesize amino acids. The enzyme MAL has exciting potential for amino acid synthesis. In its natural form, MAL catalyzes ammonia addition to 2-methylfumaric acid producing 3-methylaspartic acid as product. Unfortunately, the enzyme displays no activity whatsoever with non-natural substrates, such as large alkylamines, complex aryloxyfumarates and unsaturated monocarboxylic acids, thereby making it unsuitable for biotechnological applications.

In his thesis, Raj describes work aimed at the structure-based engineering of MAL to enhance its diastereoselectivity and expand its substrate scope. Examples are reported where he has successfully altered the diastereoselectivity of the wild-type enzyme and exploited the engineered variants of MAL for the stereoselective synthesis of optically pure aspartic acid derivatives. In addition, he has successfully engineered the substrate scope of MAL and demonstrated the usefulness of the engineered enzymes for the synthesis of various novel derivatives of aspartic acid.

This newly developed biocatalytic methodology provides exciting opportunities for clean and environmentally friendly synthesis of a large variety of substituted aspartic acids, which are valuable as tools for neurobiological research and as chiral building blocks for pharma- and neutraceuticals.