Ergosteroids: induction of thermogenic enzymes in liver of rats treated with steroids derived from dehydroepiandrosterone.

Dehydroepiandrosterone (DHEA), an intermediate in the biosynthesis of testosterone and estrogens, exerts several physiological effects not involving the sex hormones. When fed to rats it induces the thermogenic enzymes mitochondrial sn-glycerol-3-phosphate dehydrogenase and cytosolic malic enzyme in their livers. Animals and humans, and their excised tissues, are known to hydroxylate DHEA at several positions and to interconvert 7 alpha-hydroxy-DHEA, 7 beta-hydroxy-DHEA, 7-oxo-DHEA, and the corresponding derivatives of androst-5-enediol. We report here that these 7-oxygenated derivatives are active inducers of these thermogenic enzymes in rats and that the 7-oxo derivatives are more active than the parent steroids. We postulate that the 7 alpha-hydroxy and 7-oxo derivatives are on a metabolic pathway from DHEA to more active steroid hormones. These 7-oxo steroids have potential as therapeutic agents because of their increased activity and because they are not convertible to either testosterone or estrogens.

Identification of a gene involved in the biosynthesis of cyclopropanated mycolic acids in Mycobacterium tuberculosis.

Mycolic acids represent a major constituent of the mycobacterial cell wall complex, which provides the first line of defense against potentially lethal environmental conditions. Slow-growing pathogenic mycobacteria such as Mycobacterium tuberculosis modify their mycolic acids by cyclopropanation, whereas fast-growing saprophytic species such as Mycobacterium smegmatis do not, suggesting that this modification may be associated with an increase in oxidative stress experienced by the slow-growing species. We have demonstrated the transformation of the distal cis double bond in the major mycolic acid of M. smegmatis to a cis-cyclopropane ring upon introduction of cosmid DNA from M. tuberculosis. This activity was localized to a single gene (cma1) encoding a protein that was 34% identical to the cyclopropane fatty acid synthase from Escherichia coli. Adjacent regions of the DNA sequence encode open reading frames that display homology to other fatty acid biosynthetic enzymes, indicating that some of the genes required for mycolic acid biosynthesis may be clustered in this region. M. smegmatis overexpressing the cma1 gene product significantly resist killing by hydrogen peroxide, suggesting that this modification may be an important adaptation of slow-growing mycobacteria to oxidative stress.

Biosynthesis and metabolism of salicylic acid.

Pathways of salicylic acid (SA) biosynthesis and metabolism in tobacco have been recently identified. SA, an endogenous regulator of disease resistance, is a product of phenylpropanoid metabolism formed via decarboxylation of trans-cinnamic acid to benzoic acid and its subsequent 2-hydroxylation to SA. In tobacco mosaic virus-inoculated tobacco leaves, newly synthesized SA is rapidly metabolized to SA O-beta-D-glucoside and methyl salicylate. Two key enzymes involved in SA biosynthesis and metabolism: benzoic acid 2-hydroxylase, which converts benzoic acid to SA, and UDPglucose:SA glucosyltransferase (EC 2.4.1.35), which catalyzes conversion of SA to SA glucoside have been partially purified and characterized. Progress in enzymology and molecular biology of SA biosynthesis and metabolism will provide a better understanding of signal transduction pathway involved in plant disease resistance.

Induced oleoresin biosynthesis in grand fir as a defense against bark beetles.

Grand fir (Abies grandis) saplings and derived cell cultures are useful systems for studying the regulation of defensive oleoresinosis in conifers, a process involving both the constitutive accumulation of resin (pitch) in specialized secretory structures and the induced production of monoterpene olefins (turpentine) and diterpene resin acids (rosin) by nonspecialized cells at the site of injury. The pathways and enzymes involved in monoterpene and diterpene resin acid biosynthesis are described, as are the coinduction kinetics following stem injury as determined by resin analysis, enzyme activity measurements, and immunoblotting. The effects of seasonal development, light deprivation, and water stress on constitutive and wound-induced oleoresinosis are reported. Future efforts, including a PCR-based cloning strategy, to define signal transduction in the wound response and the resulting gene activation processes are delineated.

A prokaryotic origin for light-dependent chlorophyll biosynthesis of plants.

Flowering plants require light for chlorophyll synthesis. Early studies indicated that the dependence on light for greening stemmed in part from the light-dependent reduction of the chlorophyll intermediate protochlorophyllide to the product chlorophyllide. Light-dependent reduction of protochlorophyllide by flowering plants is contrasted by the ability of nonflowering plants, algae, and photosynthetic bacteria to reduce protochlorophyllide and, hence, synthesize (bacterio) chlorophyll in the dark. In this report, we functionally complemented a light-independent protochlorophyllide reductase mutant of the eubacterium Rhodobacter capsulatus with an expression library composed of genomic DNA from the cyanobacterium Synechocystis sp. PCC 6803. The complemented R. capsulatus strain is capable of synthesizing bacteriochlorophyll in the light, thereby indicating that a chlorophyll biosynthesis enzyme can function in the bacteriochlorophyll biosynthetic pathway. However, under dark growth conditions the complemented R. capsulatus strain fails to synthesize bacteriochlorophyll and instead accumulates protochlorophyllide. Sequence analysis demonstrates that the complementing Synechocystis genomic DNA fragment exhibits a high degree of sequence identity (53-56%) with light-dependent protochlorophyllide reductase enzymes found in plants. The observation that a plant-type, light-dependent protochlorophyllide reductase enzyme exists in a cyanobacterium indicates that light-dependent protochlorophyllide reductase evolved before the advent of eukaryotic photosynthesis. As such, this enzyme did not arise to fulfill a function necessitated either by the endosymbiotic evolution of the chloroplast or by multicellularity; rather, it evolved to fulfill a fundamentally cell-autonomous role.

Evolution of alkaloid biosynthesis in the genus Narcissus

In an attempt to reveal the relationships between alkaloid biosynthesis and phylogeny, we investigated by GC–MS the alkaloid patterns of 22 species and 3 hybrids (from 45 locations) from seven main sections of the genus Narcissus (Amaryllidaceae). The results indicate that the first alkaloids to evolve in the genus Narcissus were of the lycorine- and homolycorine-type. The alkaloid pattern of the Nevadensis section supports its recent separation from the Pseudonarcissus section. The plants of Narcissus pallidulus (Ganymedes section) show a predominance of Sceletium-type compounds, which are quite rare in the Amaryllidaceae family. Two successful evolutionary strategies involving alkaloid biosynthesis and leading to an expansion in taxa and occupied area were determined. Firstly, a diversification of alkaloid patterns and a high alkaloid concentration in the organs of the large Narcissus species (in the Pseudonarcissus section) resulted in an improved chemical defence in diverse habitats. Secondly, both plant size and alkaloid biosynthesis were reduced (in the Bulbocodium and Apodanthi sections) relegated to dry pastures and rocky places.

Isotopes in biochemistry and biosynthesis of labeled compounds; a selected list of references.

Cover title.

Tagged atom method of studying the biosynthesis of chlorophyll (Metod mechenych atomov v izuchenii biosinteza chlorofilla)

Translated from a publication of the Academy of Sciences, of Belorussiya, S.S.R., Minsk, 1956.

Design and operation of a carbon-14 biosynthesis chamber /

Cover title.

Advanced precursors in marine biosynthetic study. Part 3: The biosynthesis of dichloroimines in the tropical marine sponge Stylotella aurantium

The biosynthetic origins of the dichloroimine group in the stylotellanes A and B 1,2 have been investigated by incorporation of [C-14]-labeled farnesyl isocyanide 7 and farnesyl isothiocyanate 3 into the sponge Stylotella aurantium. (C) 2002 Elsevier Science Ltd. All rights reserled.

Characterization of Pantoea dispersa UQ68J: producer of a highly efficient sucrose isomerase for isomaltulose biosynthesis

Aims: Isolation, identification and characterization of a highly efficient isomaltulose producer. Methods and Results: After an enrichment procedure for bacteria likely to metabolize isomaltulose in sucrose-rich environments, 578 isolates were screened for efficient isomaltulose biosynthesis using an aniline/diphenylamine assay and capillary electrophoresis. An isolate designated UQ68J was exceptionally efficient in sucrose isomerase activity. Conversion of sucrose into isomaltulose by UQ68J (enzyme activity of 90-100 U mg(-1) DW) was much faster than the current industrial strain Protaminobacter rubrum CBS574.77 (41-66 U mg(-1) DW) or a reference strain of Erwinia rhapontici (0.3-0.9 U mg(-1) DW). Maximum yield of isomaltulose at 78-80% of supplied sucrose was achieved in less than half the reaction time needed by CBS574.77, and the amount of contaminating trehalulose (4%) was the lowest recorded from an isomaltulose-producing microbe. UQ68J is a Gram negative, facultatively anaerobic, motile, noncapsulate, straight rod-shaped bacterium producing acid but no gas from glucose. Based on 16S rDNA analysis UQ68J is closest to Klebsiella oxytoca, but it differs from Klebsiella in defining characteristics and most closely resembles Pantoea dispersa in phenotype. Significance and Impact of Study: This organism is likely to have substantial advantage over previously characterized sucrose isomerase producers for the industrial production of isomaltulose.

Marine isocyanides and related natural products structure, biosynthesis and ecology

This review highlights structural and biosynthetic work on a group of nitrogen-functionalised terpenes that are almost exclusively found in marine invertebrates and the animals that feed on them. The chemical functionality reviewed includes isocyanides, isothiocyanates, formamides, thiocyanates, isocyanates, and dichloroimines. The literature through mid 2003 is reviewed and there are 143 citations.

Hepatic urea biosynthesis in the euryhaline elasmobranch Carcharhinus leucas

Plasma urea levels and hepatic urea production in the euryhaline bull shark, Carcharhinus leucas, acclimated to freshwater and seawater environments were measured. It was found that plasma urea concentration increased with salinity and that this increase was, in part, the result of a significant increase in hepatic production of urea. This study provides direct evidence that hepatic production of urea plays an important role in the osmoregulatory strategy of C. leucas.

Spiroacetal biosynthesis: ()-1,7-dioxaspiro[5.5]undecane in Bactrocera cacuminata and Bactrocera oleae (olive fruit fly)

[GRAPHICS] A biosynthetic scheme rationalizing the formation of (+/-)-1,7-dioxaspiro[5.5]undecane (5) in the fruit fly species Bactrocera cacuminata and Bactrocera oleae (olive fruit fly) is presented. Incorporation studies with deuterium-labeled keto aldehyde (10), 1,5-nonanediol (11), and 1,5,9-nonanetriol (12), and our previous finding that both oxygen atoms of 5 originate from dioxygen, are strongly evidentiary. The racemic condition of the natural spiroacetal 5 is accounted for, and inter alia, it is demonstrated that dihydropyran (18) is not an important intermediate en route to 5.

Testosterone secretion and pharmacological spermatozoal recovery in the cane toad (Bufo marinus)

The cane toad (Bufo marinus) was used as a model to study male anuran reproductive endocrinology and to develop a protocol for non-invasive sperm recovery. Circulating testosterone concentrations in 6-hourly samples did not vary significantly (P < 0.05) over a 24 h period although there was a tendency (P = 0.06) for testosterone to be elevated at 19:00 h relative to other times of the day, which may be related to the nocturnal activity pattern of this species. Testosterone secretion after intraperitoneal (IP) injection of either a GnRH agonist (5 mu g IP) or hCG (1000 IU) was also examined. While the GnRH agonist did not produce a significant increase above basal plasma testosterone (0.29, 95% C.I. of 0.05-1.10 ng/ml), injection of hCG resulted in an increase (P < 0.01) of plasma testosterone with peak concentrations at approximately 120 min (4.17, 95% C.I. of 2.69-7.44 ng/ml) after injection. Non-invasive pharmaceutical sperm recovery was attempted following IP injection of graded doses of GnRH agonist, hCG or FSH. Urine was collected at 3, 6 and 12 h after treatment to assess sperm quality and quantity. The optimal protocol for sperm recovery in cane toads was injection of either 1000 or 2000 IU hCG; there was no significant difference in the quality of the spermic urine samples obtained using either dose of hCG or with respect to collection time. The findings indicated that hCG can be used to assess testicular steroidogenic status and also to induce sperm recovery in the cane toad. The hCG protocols developed in this study will have application in studies on the reproductive biology of rare and endangered male anurans. (c) 2005 Elsevier B.V. All rights reserved.