Dehydrodinosterol,dinosterone and related sterols of a non-photosynthetic dinoflagellate, Crypthecodinium cohnii

The heterotrophic dinoflagellate Crypthecodinium cohnii contained the 4α-methyl sterols, dinosterol, dehydrodinosterol (4α,23,24-trimethylcholesta-5,22-dien-3β-ol) and the tentatively identified 4α,24-dimethyl-cholestan-3β-ol and 4α,24-dimethylcholest-5-en-3β-ol. The major 4-demethyl sterol was cholesta-5,7-dien-3β-ol which was accompanied by a smaller amount of cholesterol and traces of several other C₂₇,C₂₈ and C₂₉ sterols. In addition, a 3-oxo-steroid fraction was isolated and the major component identified as dinosterone (4α,23,24-trimethylcholest-22-en-3-one). The possible biosynthetic relationships of these compounds are discussed.     

Sitosterol biosynthesis in Hordeum vulgare

Excised barley embryos cultured on a nutrient medium containing methionine-[CD₃] incorporated deuterium into the newly biosynthesized sterols. Two deuterium atoms were present in 24-methylenecycloartanol, 24-methylenelophenol and campesterol and a maximum of four deuterium atoms were incorporated into 24-ethylidenelophenol, stigmasterol and sitosterol. Mevalonic acid-[2-¹⁴C(4R)4-³H₁] was utilized by the barley embryos to give 28-isofucosterol with a ³H-¹⁴C atomic ratio of 3:5 and stigmasterol and sitosterol with a ³H-¹⁴C atomic ratio of 2:5. 24-Methylenelophenol and 24-ethylidenelophenol were isolated from barley seed and 24-ethylidenelophenol-[2,4-³H₃] was incorporated into sitosterol by barley seedlings. These results show that in the production of sitosterol a 24-ethylidenesterol intermediate is produced and it is suggested that this is isomerized to give a Δ^24,(25) sterol prior to reduction to the saturated C₂₉ sterol side chain.     

Glucofructosan biosynthesis in Fusarium oxysporum

Low MW glucofructosans have been detected in the medium of Fusarium oxysporum. A 53-fold purification of fructosyl transferase has been achieved by ethanol precipitation, DEAE-cellulose and Sephadex G-100 column chromatography. Maximum fructosyl transferase activity coincided with maximum glucofructosan concentration in the medium. Invertase showed greatest activity in the later stages of growth when glucofructosans were absent. Fructosyl transferase and invertase have been separated by DEAE-cellulose column chromatography. On the basis of kinetic studies and effect of nucleotides on fructosyl transferase in the presence and absence of MgCl₂, a two site active centre linked through a nucleotide bridge is proposed. Fructosyl transferase and invertase are highly phosphorylated.     

Furanocoumarin biosynthesis in Ruta graveolens cell cultures

The biosynthetic routes to four linear furanocoumarins—psoralen, xanthotoxin, bergapten. isopimpinellin-co-occurring in Ruta graveolens cell cultures have been investigated with six ¹⁴C-labelled compounds. Mevalonic acid was only poorly incorporated, in contrast to umbelliferone. In support of previous suggestions, 7-demethylsuberosin and (±)-marmesin were very good precursors of the linear furanocoumarins. 7-O-Prenylumbelliferone also was fairly well utilized, but this was probably owing to a prior ether cleavage yielding umbelliferone. Psoralen was well incorporated into bergapten and xanthotoxin, but not into the dimethoxylated isopimpinellin. Differences exist between the organized plant and its cell culture in terms of metabolic products and, by implication, precursor utilization. S(+)-Marmesin was obtained in small quantity from an acid-hydrolysable conjugate present in the culture medium. Syntheses of [2-¹⁴C]7-demethylsuberosin, [2-¹⁴C]osthenol, [2-¹⁴C]7-O-prenylumbelliferone, [3-¹⁴C] (±)-marmesin, and [3-¹⁴C]psoralen are described, as well as an improved method for separation of furanocoumarin mixtures by TLC and GLC.     

Methionine biosynthesis in isolated Pisum sativum mitochondria

Homocysteine-dependent transmethylases utilizing 5-methyltetrahydropteroylglutamic acid and S-adenosylmethionine as methyl donors have been examined using ammonium sulphate fractions prepared from isolated mitochondria of pea cotyledons. Substantial levels of a 5-rnethyltetrahydropteroylglutamate transmethylase were detected, the catalytic properties of this enzyme being found similar to those of a previously reported enzyme present in cotyledon extracts. The mitochondrial 5-CH₃-H₄PteGlu transmethylase had an apparent K_m of 25 μM for the methyl donor, was saturated with homocysteine at 1 mM and was inhibited 50% by l-methionine at 2.5 mM. At similar concentrations of methyl donor the mitochondrial S-adenosylmethionine methyltransferase was not saturated. Mitochondrial preparations were found capable of synthesizing substantial amounts of S-adenosylmethionine but lacked ability to form S-methylmethionine. Significant levels of β-cystathionase, cystathionine-γ-synthase, l-homoserine transacetylase and l-homoserine transsuccinylase were detected in the isolated mitochondria. The activity of the enzymes of homocysteine biosynthesis was not affected by l-methionine in vitro. It is concluded that pea mitochondria have ability to catalyze the synthesis of methionine de novo.     

Squalene biosynthesis by a cell-free extract of Rhizopus arrhizus

Squalene was identified as the principal radioactive component (85%) of the hexane-soluble products formed from mevalonate-[2-¹⁴C] by a cell-free preparation from Rhizopus arrhizus. The system required ATP, NADH and Mn²⁺ to obtain 20–40% incorporation of the substrate into squalene. Temperature and pH optima for the system were 20° and 7.0, respectively.     

Ketocarotenoid biosynthesis by Haematococcus lacustris

Haematococcus lacustris incubated on a nutrient-depleted medium utilised acetate-[2-¹⁴C] from the medium and carbon fixed photosynthetically for the biosynthesis of ketocarotenoids. Conversion of β-carotene to astaxanthin occurs via the intermediates echinenone and canthaxanthin.     

Dormantinol,a possible precursor in solanidine biosynthesis,from budding Veratrum grandiflorum

A new sapogenin, dormantinol, was isolated from budding Veratrum, and identified as (25S)-cholest-5-ene-3β,22α,26-triol by spectral analysis and its synthesis from dormantinone. Cholesterol was also identified in the budding Veratrum.     

Biosynthese des ramifications en C-24 des phytosterols de Physarum polycephalum et d'Ochromonas danica

The side chain C-24 alkylation mechanism of phytosterols of Physarum polycephalum and Ochromonas danica, cultured in a nutrient medium containing methionine-CD₃, has been studied. Depending on species, five or four deuterium atoms were incorporated respectively in C-24 ethyl phytosterols. No relation could be established between the stereochemistry of C-24 and the alkylation mechanism at this position.     

Sterol biosynthesis via cycloartenol in Saprolegnia

The Oomycete Saprolegnia ferax incorporates ³H from both cycloartenol-[2-³H] and lanosterol-[2-³H] into its normal sterols cholesterol, fucosterol, desmosterol, and 24-methylenecholesterol. It is concluded that sterol biosynthesis in this organism is via cycloartenol and the taxonomic implications are discussed.     

Alkaloid biosynthesis in Croton flavens

The biosynthesis of the morphinandienone alkaloids norsinoacutine, sinoacutine and flavinantine has been studied using 1-³ H-sinoacutine, 1-³H-norsinoacutine, 1-³H-norsinoacutinols, l-[S-methyl-¹⁴C]-methionine, glycine-2-¹⁴C, 1-³H-8,14-dihydronorsalutaridine, 1-³ H-8,14-dihydrosalutaridine, 1-³H-sinomenine, 1-³H-isosinomenine, (±)-[2-¹⁴C]phenylalanine, (±)-[N-methyl-¹⁴C]orientaline and (±)-[N-methyl-¹⁴C]reticuline.     

Galactolipid biosynthesis in Zea mays shoots

Illumination of dark-grown maize seedlings produced an increase in their mono- and di-galactosyl contents with the two galactose moieties being donated by UDP-galactose. Diolein was an effective exogenous acceptor of the first galactosylation and endogenous maize mono-galactosyl diglyceride of the second.     

The biosynthesis of melanin in Alternaria

A melanin which is insoluble in strong alkali has been isolated from Alternaria mycelium. Alkali fusion of the pigment produced p-hydroxybenzoa     

In vitro and in vivo biosynthesis of xanthophylls by the cyanobacterium Aphanocapsa

Of the six carotenoids identified in the cyanobacterium Aphanocapsa, β-carotene, zeaxanthin, echinenone and myxoxanthophyll are the major pigments, whilst β-cryptoxanthin and 3-hydroxy-4-keto-β-carotene are present only in trace amounts. With the exception of zeaxanthin, the other xanthophylls could be formed in vitro from [¹⁴C]phytoene in high yields, especially β-cryptoxanthin and 3-hydroxy-4-keto-β-carotene. In a time course experiment of xanthopyll biosynthesis the flow of radioactivity from [¹⁴C]phytoene was followed through the pools of phytofluene, lycopene, and β-carotene. The reaction sequence from phytoene to xanthophylls is sensitive in vitro to both difunone, an inhibitor of carotene desaturation, and CPTA, an inhibitor of cyclization.     

In vivo biosynthesis of tribromoheptene oxide in Bonnemaisonia nootkana

Experimental evidence is presented supporting the involvement of acetate and palmitate in the biosynthesis of tribromoheptene oxide in this red alga.     

生物合成长链二元酸新产业的崛起

长链二元酸是一类用途极其广泛的重要精细化工产品。综述了长链二元酸的用途、来源,国内外研究概况以及产业化现状。说明生物合成长链二元酸是中国正在崛起的新产业。     

New bioregulators of gibberellin biosynthesis in Gibberella fujikuroi

A number of new inhibitors of gibberellin (GA) biosynthesis in Gibberella fujikuroi are reported, including secondary, tertiary and quaternary amines. Octyltrimethylammonium iodide and 3-chloropropyltrimethylammonium iodide were equally as effective as 2-chloroethyltrimethylammonium chloride (CCC). At least two of the other inhibitors reported, diethyloctylamine hydrochloride and octyltriethylammonium iodide, showed a different pattern of accumulation of GAs and kaurenoic acids than did CCC.     

Cyanoglucoside biosynthesis in white clover (Trifolium repens)

l-valine-(U-¹⁴C), isobutyraldoxime-(U-¹⁴C) and 2-hydroxyisobutyraldoxime-(1,3-¹⁴C) were fed to white clover shoots which contained or lacked cyanoglucoside. Labelling results indicated that plants which were unable to synthesize linamarin from these precursors lacked the ability to glucosylate 2-hydroxyisobutyronitrile. When l-valine-(U-¹⁴C) was fed to cyanoglucoside-producing plants in the presence of cold isobutyraldoxime, radioactivity could be trapped in this compound. No radioactivity was trapped in isobutyraldoxime fed to non-cyanoglucoside-producing shoots demonstrating that this phenotype also lacks the ability to convert valine into the aldoxime. This suggests that the non-cyanoglucoside-producing plants have at least two steps in the biosynthesis of linamarin missing. Differences between the linamarin biosynthetic enzymes of white clover and flax were demonstrated using the inhibitor O-methylthreonine and by the failure of cyanoglucoside-producing white clover shoots to synthesize linamarin from fed 2-hydroxyisobutyraldoxime.     

Structure and biosynthesis of a new anthraquinone from Streptocarpus dunnii

A new anthraquinone (1-hydroxy-2-hydroxymethylanthraquinone has been isolated from the title plant. The structure was determined by spectroscopy and synthesis. Investigation on the biosynthesis showed that this quinone is formed via o-succinoylbenzoic acid.     

Chlorogenic acid biosynthesis in Cestrum poeppigii

The chlorogenic acid content of Cestrum poeppigii, and its ability to form the acid from labelled t-cinnamic acid, was determined at different stages of growth. In contrast to mature plants, young plants showed great seasonal variation in their chlorogenic acid content. The incorporation of radioactivity from t-cinnamic into chlorogenic acid also differed greatly during the growth period. Trapping experiments with caffeic and p-coumaric acids were performed to study the effect of large pools of these acids on the incorporation of t-cinnamic acid-3-[¹⁴C] into chlorogenic acid. The kinetics of incorporation exclude a major role for caffeic acid in the biosynthesis of chlorogenic acid.