pyrophosphate and isoprene

Isoprene is emitted by some plants and is the most abundant biogenic hydrocarbon entering the atmosphere. Multiple studies have elucidated protective roles of isoprene against several environmental stresses, including high temperature, excessive ozone, and herbivory attack. However, isoprene emission adversely affects atmospheric chemistry by contributing to ozone production and aerosol formation. Thus, understanding the regulation of isoprene emission in response to varying environmental conditions, for example, elevated CO

Topics: Butadienes; Carbon Dioxide; Diphosphates; Hemiterpenes; Ozone; Pentanes; Photosynthesis; Plant Leaves; Plants; Populus

A cyclolavandulyl group is a C10 monoterpene with a branched and cyclized carbon skeleton. This monoterpene is rarely found in nature, and its biosynthesis is poorly understood. To determine the biosynthesis mechanism of this monoterpene, we sequenced the genome of Streptomyces sp. CL190, which produces lavanducyanin, a phenazine with an N-linked cyclolavandulyl structure. Sequencing and homology searches identified one candidate gene product that consists of only a cis-isoprenyl diphosphate synthase domain. Disruption of the gene and biochemical analysis of the recombinant enzyme demonstrated that the enzyme synthesized a cyclolavandulyl diphosphate essential for the biosynthesis of lavanducyanin. This enzyme is an unprecedented terpene synthase that catalyzes both the condensation of the C5 isoprene units and subsequent cyclization to form the cyclolavandulyl monoterpene structure.

Topics: Alkyl and Aryl Transferases; Base Sequence; Butadienes; Cyclization; Diphosphates; Genes, Bacterial; Hemiterpenes; Monoterpenes; Pentanes; Phenazines; Streptomyces

Farnesyl diphosphate (FPP) synthase catalyzes the consecutive head-to-tail condensations of isopentenyl diphosphate (IPP, C5) with dimethylallyl diphosphate (DMAPP, C5) and geranyl diphosphate (GPP, C10) to give (E,E)-FPP (C15). The enzyme belongs to a genetically distinct family of chain elongation enzymes that install E-double bonds during each addition of a five-carbon isoprene unit. Analysis of the C10 and C15 products from incubations with avian FPP synthase reveals that small amounts of neryl diphosphate (Z-C10) and (Z,E)-FPP are formed along with the E-isomers during the C5 --> C10 and C10 --> C15 reactions. Similar results were obtained for FPP synthase from Escherichia coli, Artemisia tridentata (sage brush), Pyrococcus furiosus, and Methanobacter thermautotrophicus and for GPP and FPP synthesized in vivo by E. coli FPP synthase. When (R)-[2-2H]IPP was a substrate for chain elongation, no deuterium was found in the chain elongation products. In contrast, the deuterium in (S)-[2-2H]IPP was incorporated into all of the products. Thus, the pro-R hydrogen at C2 of IPP is lost when the E- and Z-double bond isomers are formed. The synthesis of Z-double bond isomers by FPP synthase during chain elongation is unexpected for a highly evolved enzyme and probably reflects a compromise between optimizing double bond stereoselectivity and the need to exclude DMAPP from the IPP binding site.

Topics: Artemisia; Binding Sites; Butadienes; Catalysis; Deuterium; Diphosphates; Diterpenes; Escherichia coli; Gas Chromatography-Mass Spectrometry; Geranyltranstransferase; Hemiterpenes; Hydrogen; Isomerism; Methanobacteriaceae; Models, Chemical; Pentanes; Polyisoprenyl Phosphates; Pyrococcus furiosus; Substrate Specificity; Time Factors