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Unlocking Iminium Catalysis in Artificial Enzymes to Create a Friedel–Crafts Alkylase
- Source :
- ACS Catalysis, 11(12), 6763-6770. AMER CHEMICAL SOC, ACS Catalysis
- Publication Year :
- 2021
- Publisher :
- American Chemical Society (ACS), 2021.
-
Abstract
- The construction and engineering of artificial enzymes consisting of abiological catalytic moieties incorporated into protein scaffolds is a promising strategy to realize non-natural mechanisms in biocatalysis. Here, we show that incorporation of the noncanonical amino acid para-aminophenylalanine (pAF) into the nonenzymatic protein scaffold LmrR creates a proficient and stereoselective artificial enzyme (LmrR_pAF) for the vinylogous Friedel-Crafts alkylation between α,β-unsaturated aldehydes and indoles. pAF acts as a catalytic residue, activating enal substrates toward conjugate addition via the formation of intermediate iminium ion species, while the protein scaffold provides rate acceleration and stereoinduction. Improved LmrR_pAF variants were identified by low-throughput directed evolution advised by alanine-scanning to obtain a triple mutant that provided higher yields and enantioselectivities for a range of aliphatic enals and substituted indoles. Analysis of Michaelis-Menten kinetics of LmrR_pAF and evolved mutants reveals that different activities emerge via evolutionary pathways that diverge from one another and specialize catalytic reactivity. Translating this iminium-based catalytic mechanism into an enzymatic context will enable many more biocatalytic transformations inspired by organocatalysis.
- Subjects :
- catalytic promiscuity
Stereochemistry
Friedel−Crafts alkylation
Context (language use)
Alkylation
010402 general chemistry
01 natural sciences
Catalysis
Residue (chemistry)
iminium ion
Reactivity (chemistry)
directed evolution
Friedel–Crafts reaction
noncanonical amino acids
biology
010405 organic chemistry
Chemistry
Artificial enzyme
Iminium
General Chemistry
Directed evolution
Combinatorial chemistry
0104 chemical sciences
Biocatalysis
Organocatalysis
biology.protein
stop-codon suppression
Stereoselectivity
artificial enzymes
Research Article
Subjects
Details
- ISSN :
- 21555435
- Volume :
- 11
- Database :
- OpenAIRE
- Journal :
- ACS Catalysis
- Accession number :
- edsair.doi.dedup.....0ee404b973099ab20b3728e3a36a089b
- Full Text :
- https://doi.org/10.1021/acscatal.1c00996