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At least 19 recordsLinked to original sources
PubMed2026

Biochemical analysis of the TPS-b subfamily reveals a cineole-centered monoterpene biosynthetic module in Medicago truncatula.

Terpenoids constitute one of the largest and most structurally diverse classes of plant specialized metabolites, with diversity generated by terpene synthases (TPSs) and downstream tailoring enzymes. In Medicago truncatula, the TPS-b subfamily comprises five putative synthases, two of which are embedded within a previously uncharacterized genomic locus containing a cytochrome P450 (CYP) and a BAHD-type acyltransferase. Here, we present a comprehensive biochemical analysis of the M. truncatula TPS-b subfamily and define a cineole-centered monoterpene biosynthetic module. Heterologous expression and in vitro assays with multiple prenyl diphosphate substrates revealed three catalytically active TPS-b enzymes with distinct substrate preferences and product profiles. MtTPS4 functions as a dedicated (E)-β-ocimene synthase, whereas MtTPS15 exhibits substrate-dependent bifunctionality, producing (E)-β-ocimene from geranyl diphosphate and α-farnesene from farnesyl diphosphate. MtTPS36 generates 1,8-cineole as the predominant product alongside α-terpineol from geranyl and neryl diphosphate. Genome analysis revealed that MtTPS36 is colocalized with a cytochrome P450 belonging to the CYP736 family. Biochemical characterization of this CYP identified a previously undescribed plant cineole hydroxylase that catalyzes oxidation of 1,8-cineole to yield 2α-hydroxy-1,8-cineole (also known as 2-exo-hydroxy-1,8-cineole), establishing a TPS-CYP biosynthetic module. These results define the gene-to-metabolite relationships within the TPS-b subfamily in M. truncatula and expand the known enzymatic biosynthetic capacity underlying oxygenated monoterpene biosynthesis in plants.

1,8-Cineole↗
PubMed1978

The effect of dietary monoterpenes on the cholesterol level of eggs.

Monoterpenes were included in the diets of laying hens in an attempt to inhibit the synthesis of cholesterol and hence reduce its amount in egg yolk. However, feeding five monoterpenes, phorone or 200 mg. cholesterol per day to hens did not significantly change the level of cholesterol in the egg yolk. These compounds did not cause signs of ill health in the hen or a decline in egg production.

Animals↗
PubMed1976

Characterization of a cytochrome P-450 dependent monoterpene hydroxylase from the higher plant Vinca rosea.

A monooxygenase isolated from 5-day old etiolated Vinca rosea seedlings was shown to catalyze the hydroxylation of the monoterpene alcohols, geraniol and nerol, to their corresponding 10-hydroxy derivatives. Hydroxylase activity was inpendent upon NADPH (neither NADH nor combination of NADH, NADP+ and ATP served as substitutes) and O2. Geraniol hydroxylation was enhanced by dithiothreitol (monothiols were less effective) and inhibited by phospholipases, thiol reagents, metyrapone, and cytochrome c, as well as other inhibitors of cytochrome P-450 systems. Geraniol was hydroxylated at a faster rate than nerol, but the alcohols possessed similar apparent Km values. The membrane-bound hydroxylase was solubilized by treatment with sodium cholate, Renex-30, or Lubrol-WX. Cholate-treated enzyme was resolved by DEAE-cellulose chromatography and reconstitution of the hydroxylase was effected utilizing different fractions containing cytochrome P-450, a NADPH-cytochrome c reductase, and lipid.

Binding Sites↗
PubMed1979

Selective oocyte degeneration and impaired fertility in rats treated with the aliphatic monoterpene, Citral.

Mature female rats treated with Citral (3-7-dimethyl-2,6-octadienal) either topically for 60 or 100 days or by 6 i.p. injections (at 4-5 day day intervals) showed a marked decrease in the number of normal follicles per section, because oocytes tended to degenerate although the follicular cells remained normal. The reproductive performance after Citral treatment was impaired: there was a reduction in implantation number and litter size and an increased post-implantation fetal wastage. None of the young survived after 100 days of topical Citral treatment. It is suggested that Citral directly affects the oocytes.

Acyclic Monoterpenes↗
PubMed1977

Metabolism of monoterpene alcohol, linalool, by a soil pseudomonad.

A microorganism of the genus Pseudomonas has been isolated from the soil by enrichment culture techniques with linalool(I) as the sole source of carbon and energy. The organism is also capable of utilizing limonene, citronellol, and geraniol as substrates but fails to grow on citral, critranellal, and 1,8-cineole. Fermentation of linalool by this bacterium in a mineral salt medium results in the formation of 10-hydroxylinalool(II), oleuropeic acid (IX), 2-vinyl-2-methyl-5-hydroxyisopropyl-tetraphydrofuran)linalool oxide, V), 2-vinyl-2-methyl-tetrahydrofuran-5-one(unsaturated lactone, VI), and few unidentified minor metabolities. Probable pathways for the biodegradation of linalool are presented.

Biodegradation, Environmental↗
PubMedDate not supplied

Behavioral and toxicological studies of cyclopentanoid monoterpenes from Nepeta cataria.

Two samples of catnip oil were analyzed by tic, gc, and hplc; the results indicated the presence of 23 components. Fractionation of the commercial sample of catnip oil by either distillation or gc yielded 40% nepetalactone and 43% nepetalic acid. Catnip oil, nepetalic acid, and a nepetalactone-enriched fraction were evaluated for toxicological and behavioral effects in mice and rats. The LD50 of catnip oil, the nepetalactone-enriched fraction, and nepetalic acid were found in mice to be: 1300 mg/kg, 1550 mg/kg and 1050 mg/kg, respectively. Catnip oil (500 mg/kg) and nepetalic acid (62.5 mg/kg) were found to significantly increase hexobarbital sleeping time in mice. Rats trained on a Sidman avoidance schedule showed a significant decrease in performance following intraperitoneal injections of catnip oil (500--750 mg/kg), nepetalic acid (125--250 mg/kg), and the nepetalactone-enriched fraction (500--750 mg/kg). Rats trained on the same avoidance schedule developed behavioral tolerance after daily injections of 750 mg/kg catnip oil.

Animals↗