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Plant Physiol

Title:		"The alpha-Terpineol to 1,8-Cineole Cyclization Reaction of Tobacco Terpene Synthases"
Author(s):		Piechulla B; Bartelt R; Brosemann A; Effmert U; Bouwmeester H; Hippauf F; Brandt W;
Address:		"Institute of Biological Sciences, Biochemistry, University of Rostock, 18059 Rostock, Germany (B.P., A.B., U.E., F.H.); birgit.piechulla@uni-rostock.de. Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany (R.B., W.B.); and birgit.piechulla@uni-rostock.de. Plant Sciences, University of Wageningen, 6708PB Wageningen, The Netherlands (H.B.) birgit.piechulla@uni-rostock.de. Institute of Biological Sciences, Biochemistry, University of Rostock, 18059 Rostock, Germany (B.P., A.B., U.E., F.H.). Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany (R.B., W.B.); and. Plant Sciences, University of Wageningen, 6708PB Wageningen, The Netherlands (H.B.)"
Journal Title:		Plant Physiol
Year:		2016
Volume:		20161011
Issue:		4
Page Number:		2120 - 2131
DOI:		10.1104/pp.16.01378
ISSN/ISBN:		1532-2548 (Electronic) 0032-0889 (Print) 0032-0889 (Linking)
Abstract:		"Flowers of Nicotiana species emit a characteristic blend including the cineole cassette monoterpenes. This set of terpenes is synthesized by multiproduct enzymes, with either 1,8-cineole or alpha-terpineol contributing most to the volatile spectrum, thus referring to cineole or terpineol synthase, respectively. To understand the molecular and structural requirements of the enzymes that favor the biochemical formation of alpha-terpineol and 1,8-cineole, site-directed mutagenesis, in silico modeling, and semiempiric calculations were performed. Our results indicate the formation of alpha-terpineol by a nucleophilic attack of water. During this attack, the alpha-terpinyl cation is stabilized by pi-stacking with a tryptophan side chain (tryptophan-253). The hypothesized catalytic mechanism of alpha-terpineol-to-1,8-cineole conversion is initiated by a catalytic dyad (histidine-502 and glutamate-249), acting as a base, and a threonine (threonine-278) providing the subsequent rearrangement from terpineol to cineol by catalyzing the autoprotonation of (S)-(-)-alpha-terpineol, which is the favored enantiomer product of the recombinant enzymes. Furthermore, by site-directed mutagenesis, we were able to identify amino acids at positions 147, 148, and 266 that determine the different terpineol-cineole ratios in Nicotiana suaveolens cineole synthase and Nicotiana langsdorffii terpineol synthase. Since amino acid 266 is more than 10 A away from the active site, an indirect effect of this amino acid exchange on the catalysis is discussed"
Keywords:		Alkyl and Aryl Transferases/chemistry/*metabolism Amino Acid Sequence Catalytic Domain Computer Simulation Cyclization Cyclohexane Monoterpenes Cyclohexanols/chemistry/*metabolism Cyclohexenes/chemistry/*metabolism Eucalyptol Monoterpenes/chemistry/*metab;
Notes:		"MedlinePiechulla, Birgit Bartelt, Richard Brosemann, Anne Effmert, Uta Bouwmeester, Harro Hippauf, Frank Brandt, Wolfgang eng 2016/10/13 Plant Physiol. 2016 Dec; 172(4):2120-2131. doi: 10.1104/pp.16.01378. Epub 2016 Oct 11"