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Publication Abstract from PubMed

We report the exploration of the evolutionary relationship between imine reductases (IREDs) and other dehydrogenases. This approach is informed by the sequence similarity between these enzyme families and the recently described promiscuous activity of IREDs for the highly reactive carbonyl compound 2,2,2-trifluoroacetophenone. Using the structure of the R-selective IRED from Streptosporangium roseum (R-IRED-Sr) as a model, beta-hydroxyacid dehydrogenases (betaHADs) were identified as the dehydrogenases most similar to IREDs. To understand how active site differences in IREDs and betaHADs enable the reduction of predominantly C = N or C = O bonds respectively, we substituted amino acid residues in betaHADs with the corresponding residues from the R-IRED-Sr and were able to increase the promiscuous activity of betaHADs for C = N functions by a single amino acid substitution. Variants betaHADAt_K170D and betaHADAt_K170F lost mainly their keto acid reduction activity and gained the ability to catalyze the reduction of imines. Moreover, the product enantiomeric purity for a bulky imine substrate could be increased from 23% ee (R-IRED-Sr) to 97% ee (betaHADAt_K170D/F_F231A) outcompeting already described IRED selectivity.

New imine-reducing enzymes from beta-hydroxyacid dehydrogenases by single amino acid substitutions.,Lenz M, Fademrecht S, Sharma M, Pleiss J, Grogan G, Nestl BM Protein Eng Des Sel. 2018 May 3. pii: 4992468. doi: 10.1093/protein/gzy006. PMID:29733377^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.