N-methyltyramine: Formation in Opuntia clavata and metabolism in Coryphantha macromeris var. Runyonii

-Administration of tyramine-[1-¹⁴C] to Opuntia clavata resulted in the formation of labeled N-methyltyramine. This procedure established the biosynthetic origin of the major alkaloid in this cactus as well as providing a radiolabeled chemical that was not commercially available. The N-methyltyramine-[1-¹⁴C] was in turn administered to Coryphantha macromeris var. runyonii to determine its metabolic role in the biosynthesis of the psychoactive cactus alkaloid normacromerine (N-methyl-3,4-dimethoxy-β-hydroxyphenethylamine). This feeding experiment established N-methyltyramine as a precursor to normacromerine.     

Directed biosynthesis of unnatural alkaloids in Dolichothele sphaerica

Using appropriate precursors, the two unnatural alkaloids 4(5)-[N-isocaproylaminomethyl]imidazole and 3-[2-N-isovalerylaminoethyl]pyrazole were produced by Dolichothele sphaerica. The former compound represents an unnatural alkaloid formed by the simultaneous introduction of two unnatural precursors, namely isocaproic acid and 4(5)-aminomethylimidazole. The latter compound represents an aberrant alkaloid formed by the introduction of a precursor of different heterocyclic entity, 3-aminoethylpyrazole.     

Biosynthesis of N-methylphenethylamine in Dolichothele sphaerica

Living Dolichothele sphaerica metabolized 1.91% of administered [2-¹⁴Clphenylalanine to N- methylphenethylamine. Phenethylamine, the presumable intermediate in this biosynthetic conversion, was detected in an extract of the cactus in very low concentrations. The addition of carrier to the extract allowed the isolation of radiolabelled phenethylamine and the establishment of its probable involvement in N- methylphenethylamine formation. This is the first report of N- methylphenethylamine biosynthesis, of phenyl- alanine serving as an efficient precursor to cactus alkaloids, and of the occurrence of phenethylamine in the Cactaceae.     

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.     

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.     

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.     

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.     

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     

尿去甲基肾上腺素/甲氧基肾上腺素测定对嗜铬细胞瘤的方法学比较

目的:通过对尿儿茶酚胺代谢产物去甲肾上腺素、甲氧基肾上腺素的测定,综合分析其对嗜铬细胞瘤的早期临床诊断价值。方法:利用酶联免疫分析法和传统柱层析法,对正常人和临床诊断为嗜铬细胞瘤及肾上腺占位病变并伴有阵发性高血压患者的24h尿去甲基肾上腺素/甲氧基肾上腺素和3-甲氧基-4-羟基苦杏仁酸(VMA)进行测定。结果:与VMA相比,24h尿去甲基肾上腺素/甲氧基肾上腺素在嗜铬细胞瘤患者中的测定值要显著高于其他肾上腺占位性病变伴高血压患者和正常人群,二者方法学有显著性差异。结论:酶联免疫分析法检测24h尿去甲基肾上腺素/甲氧基肾上腺素具有灵敏度高、特异性好的特点,为临床从肾上腺占位性病变并伴有阵发性高血压患者中筛查嗜铬细胞瘤提供了一种有价值的参考方法。     

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.     

Structure and biosynthesis of malloprenols from Mallotus japonicus

The mallo prenol isolated from the leaves of Mallotus japonicus was elucidated to be a mixture of (2Z,6Z, 10Z, 14Z, 18Z, 22Z, 26E, 30E, 34E)-3,7,11,15,19,23,27,31,35,39-decamethyl-2,6,10,14,18,22,26,30,34,38-tetracontadecaen-1-ol and its C₄₅- and C₅₅-homologues and not the previously reported structure. The malloprenols were demonstrated to be biosynthesized by successive cis condensation of isoprene residues with (2E, 6E, 10E)-geranylgeranyl pyrophosphate.     

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.     

Gibberellin estimation and biosynthesis in germinating Hordeum distichon

Gibberellic acid (GA₃) and 13-deoxy-gibberellic acid (GA₇) were identified in extracts of germinating barley as their ¹⁴C-methyl esters. The maximal level of GA₃ was estimated by an isotopic dilution procedure to be 1·5 ng per grain. Germinating barley incorporated 2-¹⁴C-mevalonic acid into several terpenes, whose specific radioactivities were measured, but incorporation into GA₃ could not be detected. Cell-free embryo extracts from germinating barley converted 2-¹⁴C-mevalonic acid into isopentenol, dimethylallyl alcohol, farnesol and squalene, while ¹⁴C-isopentenyl pyrophosphate was incorporated into geraniol, farnesol, geranylgeraniol and squalene. There was no detectable incorporation into the gibberellin intermediate ent-kaurene.     

Metabolism of phenylpropanoids in Hydrangea serrata var. thunbergii and the biosynthesis of phyllodulcin

DL-Phenylalanine-[3-¹⁴C] and cinnamic acid-[3-¹⁴C] were fed to this plant and the label from cinnamic acid was incorporated into gallic acid, phyllodulcin and quercetin. By feeding p- coumaric acid-[U-³H], caffeic acid-[U-³H] and hydrangea glucoside A-[U-³H], it was possible to show that hydroxylation at C-3′in phyllodulcin occurs after the ring closure of dihydroisocoumarin. The biosynthetic pathway of phyllodulcin in this plant is thus: phenylalanine → cinnamic acid → p- coumaric acid → hydrangenol → phyllodulcin.     

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.     

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.