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Publication Abstract from PubMed

Most terpene synthases (TPSs) contain plasticity residues that are responsible for diversified terpene products and functional evolution, which provide a potential for improving catalytic efficiency. Artemisinin, a sesquiterpene lactone from Artemisia annua L., is widely used for malaria treatment and progress has been made in engineering the production of artemisinin or its precursors. Here, we report a new sesquiterpene synthase from A. annua, alpha-bisabolol synthase (AaBOS), which has high sequence identity to amorpha-4,11-diene synthase (AaADS), a key enzyme in artemisinin biosynthesis. Comparative analysis of the two enzymes by domain-swapping and structure-based mutagenesis led to the identification of several plasticity residues, whose alteration changed the product profile of AaBOS to include gamma-humulene as the major product. To elucidate the underlying mechanisms, we solved the crystal structures of AaBOS and a gamma-humulene-producing AaBOS mutant (AaBOS-M2). Among the plasticity residues, position 399, located in the substrate binding pocket, is crucial for both enzymes. In AaBOS, substitution of Leu with Thr (AaBOSL339T) is required for gamma-humulene production; whereas in AaADS, replacing the Thr with Ser (AaADST399S) resulted in a substantial increase of the activity of amorpha-4,11-diene production, likely as a result of accelerated product release. Our work demonstrates that substitution of plasticity residues holds a potential for improving catalytic efficiency of the enzyme.

Rational engineering plasticity residues of sesquiterpene synthases from Artemisia annua: product specificity and catalytic efficiency.,Li JX, Fang X, Zhao Q, Ruan JX, Yang CQ, Wang LJ, Miller DJ, Faraldos JA, Allemann RK, Chen XY, Zhang P Biochem J. 2013 Feb 26. PMID:23438177^[1]

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