Evidence for an elongation/reduction/C1-elimination pathway in the biosynthesis of the n-heptane in xylem of Jeffrey pine

• Published in: Plant physiology (Bethesda) Vol. 111; no. 4; pp. 1263 - 1269
• Main Authors: Savage, T.J. (Washington State University, Pullman, WA.), Hristova, M.K, Croteau, R
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.08.1996
• Subjects: ACIDE ACETIQUE; ACIDO ACETICO; Aldehydes; Alkanes; AMINAS; AMINE; Biochemistry and Enzymology; Biological and medical sciences; BIOSINTESIS; BIOSYNTHESE; Biosynthesis; CARBONE; CARBONO; Esters; Fatty acids; Fundamental and applied biological sciences. Psychology; HIDROCARBUROS; Hydrocarbons; HYDROCARBURE; INHIBIDORES DE ENZIMAS; INHIBITEUR D'ENZYME; ISOTOPE RADIOACTIF; Lipids; MECANISME DE DEFENSE; MECANISMOS DE DEFENSA; Metabolism; Metabolism. Physicochemical requirements; Oximes; Pentanes; PINUS JEFFREYI; Plant physiology and development; POLIMERIZACION; POLYMERISATION; RADIOISOTOPOS; REACCIONES QUIMICAS; REACTION CHIMIQUE; THIOL; TIOLES; VIA BIOQUIMICA DEL METABOLISMO; VOIE BIOCHIMIQUE DU METABOLISME; XILEMA; Xylem; XYLEME; Xylem; Enzyme; Biosynthesis; Metabolic pathway; Synthase; Metabolic inhibitor; Heptane; Pinus jeffreyi; Regulation(control); Softwood forest tree; Gymnospermae; Coniferales; Spermatophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.111.4.1263

The biosynthetic pathway to n-heptane was investigated by examining the effect of the beta-keto acyl-acyl carrier protein synthase inhibitor (2R,3S)-2,3-epoxy-4-oxo-7E,10E -dodecadienamide (cerulenin), a thiol reagent (beta-mercaptoethanol), and an aldehyde-trapping reagent (hydroxylamine) on the biosynthesis of n-[14C]heptane and putative intermediates in xylem sections of Jeffrey pine (Pinus jeffreyi Grev. and Balf.) incubated with [14C]acetate. Cerulenin inhibited C18 fatty acid biosynthesis but had relatively little effect on radiolabel incorporation into C8 fatty acyl groups and n-heptane. beta-Mercaptoethanol inhibited n-heptane biosynthesis, with a corresponding accumulation of radiolabel into both octanal and 1-octanol, whereas hydroxylamine inhibited both n-heptane and 1-octanol biosynthesis, with radiolabel accumulation in octyl oximes. [14C]Octanal was converted to both n-heptane and 1-octanol when incubated with xylem sections, whereas [14C]1-octanol was converted to octanal and n-heptane in a hydroxylamine-sensitive reaction. These results suggest a pathway for the biosynthesis of n-heptane whereby acetate is polymerized via a typical fatty acid synthase reaction sequence to yield a C8 thioester, which subsequently undergoes a two-electron reduction to generate a free thiol and octanal, the latter of which alternately undergoes an additional, reversible reduction to form 1-octanol or loss of C1 to generate n-heptane