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Crystal Structure of (+)-Limonene Synthase from Citrus sinensis
Structural highlights
FunctionRLC1_CITSI Catalyzes the conversion of geranyl diphosphate to (+)-(4R)-limonene (PubMed:28272875, PubMed:28272876). Produces exclusively the (+)-enantiomer (PubMed:28272875). Can use neryl diphosphate as substrate (PubMed:28272876). Has no activity with farnesyl diphosphate (PubMed:28272875).[1] [2] Publication Abstract from PubMedTerpenes make up the largest and most diverse class of natural compounds and have important commercial and medical applications. Limonene is a cyclic monoterpene (C10) present in nature as two enantiomers, (+) and (-), which are produced by different enzymes. The mechanism of production of the (-)-enantiomer has been studied in great detail, but to understand how enantiomeric selectivity is achieved in this class of enzymes, it is important to develop a thorough biochemical description of enzymes that generate (+)-limonene, as well. Here we report the first cloning and biochemical characterization of a (+)-limonene synthase from navel orange (Citrus sinensis). The enzyme obeys classical Michaelis-Menten kinetics and produces exclusively the (+)-enantiomer. We have determined the crystal structure of the apoprotein in an "open" conformation at 2.3 A resolution. Comparison with the structure of (-)-limonene synthase (Mentha spicata), which is representative of a fully closed conformation (Protein Data Bank entry 2ONG ), reveals that the short H-alpha1 helix moves nearly 5 A inward upon substrate binding, and a conserved Tyr flips to point its hydroxyl group into the active site. Functional and Structural Characterization of a (+)-Limonene Synthase from Citrus sinensis.,Morehouse BR, Kumar RP, Matos JO, Olsen SN, Entova S, Oprian DD Biochemistry. 2017 Mar 15. doi: 10.1021/acs.biochem.7b00143. PMID:28272875[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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