5′-Monohydroxyphylloquinone from Anacystis and Euglena

The monohydroxy analogue of phylloquinone found in Anacystis nidulans and Euglena gracilis has been characterized as 5′-monohydroxyphylloquinone by MS analysis.     

Ein neuer Sittich aus Brasilien:Aratinga cactorum para?nsis, subsp. nova

Ohne Zusammenfassung     

Grindelane diterpenoids from Grindelia campórum and Chrysothamnus paniculatus

The structures of nine grindelic acid related diterpenes isolated as methyl esters from Grindelia camporum and Chrysothamnus paniculatus, were elucidated based on their spectral properties.     

New α-pyrones from Iboza riparia

The structures for umuravumbolide, 5,6-dihydro-6-(3-acetoxy-1-heptenyl)-2-pyrone, a new α-pyrone from Iboza riparia (Labiatae) and its corresponding deacylated product have been established. Deacetylboronolide was also isolated and identified by different spectroscopic techniques.     

Six 2′-hydroxyflavonols from Gutierrezia microcephala

Six 2′-hydroxyflavonols were isolated from Gutierrezia microcephala, including four new compounds, 5,7,2′-trihydroxy-3,6,4′,5′-tetramethoxyflavone, 5,7,2′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,2′-dihydroxy-3,6,7,8,4′,5′-hexamethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,8,5′-trimethxoyflavone and two known compounds, 5,7,2′,5′-tetrahydroxy-3,6,8,4′-tetramethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone.     

Xanthonolignoids from Kielmeyera and Caraipa species—13C NMR spectroscopy of xanthones

Kielcorin and the cadensins A and B, isolated respectively from Kielmeyera coriacea and Caraipa densiflora (Guttiferae), were shown to be xanthonolignoids. The structure of (5S,6S)-6(or 5)-hydroxymethyl-5(or 6)-(4″-hydroxy-3″-methoxyphenyl)-2,3:3′,4′-(2′-methoxyxanthono)-1,4-dioxane was proposed for kielcorin by analysis of high resolution MS and PMR spectra. The carbon shifts of xanthone were assigned and used in the ¹³C NMR spectral confirmation of the proposed structure.     

(+)-9α-Hydroxymatrine from Sophora macrocarpa

A new quinolizidine alkaloid, (+)-9α-hydroxymatrine, was isolated from the leaves of Sophora macrocarpa. Its structure was determined by a combination of spectroscopic methods, among which nuclear Overhauser enhancement experiments played a crucial role. Some generalizations are made regarding the mass spectra of matrinoids.     

N′-isopropylnornicotine: Its formation from nicotine in aged leaves of Nicotiana tabacum

An aqueous solution of nicotine-[2′-¹⁴C] was painted on the leaves of 4-month-old tobacco plants (Nicotiana tabacum) which were harvested 3 weeks later. This tracer was similarly applied to excised tobacco leaves which were allowed to dry in air for 4 weeks. The alkaloids, were extracted with the addition of N′-isopropylnornicotine, a compound which has been previously isolated from air-cured tobacco. Radioactive nicotine and nornicotine were isolated from the intact plants with only minute activity in the N′-isopropylnornicotine. All three of these alkaloids were radioactive from the air-cured leaves, and degradation of the labelled N'-isopropylnornicotine indicated that all the activity was located at the C-2′ position. A higher level of activity was found in N′-isopropylnornicotine which was obtained from excised leaves which were fed the nicotine- [2′- ¹⁴C] in aqueous acetone, and were treated on subsequent days with aqueous acetone. These results are consistent with the hypothesis that N′-isopropylnornicotine is produced in the curing of tobacco leaves by reaction of nornicotine (formed by the demethylation of nicotine) with acetoacetate, followed by decarboxylation and reduction. The ¹³C NMR chemical shifts of the methyl groups of N′-isopropylnornicotine and related 1-isopropylpyrrolidines which have chirality at the α-position of the pyrrolidine ring, are significantly different (up to 7.5 ppm).     

Candida species in tchapalo and bangui, two traditional alcoholic beverages from Côte d'Ivoire

The increase of infections due to non-Candida albicans species made it very necessary to conduct adequate characterization to be able to identify the species of Candida isolated from traditional fermented foods. In this study, based on their hue on Candida Chromogenic Agar medium, a total of 136 yeast strains were isolated from tchapalo and bangui. Molecular identification based on PCR-RFLP of internal transcribed spacers of rDNA (ITS) and sequencing of the ITS and the D1/D2 regions allowed us to assign these isolates to seven species: Candida tropicalis, Candida inconspicua, Candida rugosa, Saccharomyces cerevisiae, Kluyveromyces marxianus, Hanseniaspora guilliermondii, Trichosporon asahii. With the respect to each beverage, six species were found among with four species are regarded as opportunistic pathogens. From these, C. tropicalis, C. inconspicua and K. marxianus were the most commonly encountered. The enzyme activities of the potential pathogens assessed using API ZYM system showed that almost strains had esterase, esterase lipase, valine and cystine arylamidase, alpha chymotrypsin, alkaline phosphatase and naphthol phosphohydrolase activities. The activity of α-glucosidase was found only in C. tropicalis and C. inconspicua strains isolated from tchapalo while β-glucosidase activity was found in all strains from tchapalo and only in C. inconspicua isolated from bangui.     

1,3-β-Glucan synthase from Citrus phloem

1,3-β-Glucan synthase activity has been demonstrated in particulate fractions of bark extracts from Mexican lime. With respect to substrate, the enzyme kinetics did not conform to the Michaelis-Menten equation. The value of the Hill coefficient was 1.2 and S_0.5 is 1.1 mM. The enzyme had an optimum pH of 7.5. Maltose, sucrose, and especially cellobiose and glucose, were enzyme activators when tested at physiological concentrations. In the presence of 15 mM MgCl₂ the enzymic activity was stimulated at 10 μM UDP-glucose but decreased at 1 mM UDP-glucose, suggesting a minor 1,4-β-glucan synthase activity.     

Production of extracellular PETase from Ideonella sakaiensis using sec-dependent signal peptides in E. coli

Poly(ethylene terephthalate) (PET) is the most commonly used polyester polymer resin in fabrics and storage materials, and its accumulation in the environment is a global problem. The ability of PET hydrolase from Ideonella sakaiensis 201-F6 (IsPETase) to degrade PET at moderate temperatures has been studied extensively. However, due to its low structural stability and solubility, it is difficult to apply standard laboratory-level IsPETase expression and purification procedures in industry. To overcome this difficulty, the expression of IsPETase can be improved by using a secretion system. This is the first report on the production of an extracellular IsPETase, active against PET film, using Sec-dependent translocation signal peptides from E. coli. In this work, we tested the effects of fusions of the Sec-dependent and SRP-dependent signal peptides from E. coli secretory proteins into IsPETase, and successfully produced the extracellular enzyme using pET22b-SP_MalE:IsPETase and pET22b-SP_LamB:IsPETase expression systems. We also confirmed that the secreted IsPETase has PET-degradation activity. The work will be used for development of a new E. coli strain capable of degrading and assimilating PET in its culture medium.     

Isolation of Desulfuromonas acetoxidans cytochrome c-551.5 from the mixed culture ‘Chloropseudomonas ethylica’

The mixed culture ‘Chloropseudomonas ethylica’ strain 2K has been grown on a medium which enhanced the yield of cytochrome c-551.5 from Desulfuromonas acetoxidans. The cytochrome was purified to homogeneity and an isoelectric point of 8.40 was determined. A determination of the amide content indicated that the cytochrome contains two more amides than previously reported.     

The α-galactosidase from Escherichia coli K12

Growth of Escherichia coli on melibiose requires the induced synthesis of α-galactoside permease and α-galactosidase. Hydrolysis of the chromogenic substrate p-nitrophenyl-σ-galactoside by whole bacteria is dependent on intact oxidative metabolism. The α-galactosidase from E. coli was isolated for the first time as a soluble enzyme. In cell-free extracts p-nitrophenyl-α-galactoside hydrolisis was observed only at high protein concentrations and the activity decreased exponentially with the square of the dilution. The reason for this behaviour was shown to be that, unlike other known α-galactosidases, the enzyme of E. coli requires NAD. For optimal activity the enzyme also requires Mn²⁺, a high concentration of 2-mercaptoethanol, and a pH of 8.1. The approximate molecular weight of the active from of α-galactosidase as determined by sedimentation in a sucrose gradient is 200 000. Due to the instability of the enzyme, its purification has not been achieved.     

Morphological variation within the Edraianthus graminifolius complex (Campanulaceae) from the central Balkan Peninsula – Evidence from multivariate statistical analysis

The Edraianthus graminifolius complex is one of the most interesting groups within the genus Edraianthus DC (Campanulaceae). The plants inhabit a variety of habitats and there is a micro-geographic and ecological differentiation of populations, accompanied by pronounced morphological variation. Hence, it is not surprising that this complex is taxonomically a very controversial group. On the one hand it is described to comprise only two to four taxa, including subspecies, and on the other, a classification comprising 23 taxa of the rank of species and subspecies has been proposed.     

The neolignans (−)-carinatone and carinatin from Virola carinata

From the bark of Virola carinata two neolignans have been isolated: (?)-carcinatone, [(2S)-1-(3′,4′-dimethoxyphenyl)-2-(3″-allyl-5″-methoxy-6″-hydroxyphenyl) propanone] and carinatin, [5-allyl-7-methoxy-3-methyl-2-(3′,4′-dimethoxyphenyl)benzofuran].     

Crystal structure of α/β-galactoside α2,3-sialyltransferase from a luminous marine bacterium, Photobacterium phosphoreum

α/β-Galactoside α2,3-sialyltransferase produced by Photobacterium phosphoreum JT-ISH-467 is a unique enzyme that catalyzes the transfer of N-acetylneuraminic acid residue from cytidine monophosphate N-acetylneuraminic acid to acceptor carbohydrate groups. The enzyme recognizes both mono- and di-saccharides as acceptor substrates, and can transfer Neu5Ac to both α-galactoside and β-galactoside, efficiently. To elucidate the structural basis for the broad acceptor substrate specificity, we determined the crystal structure of the α2,3-sialyltransferase in complex with CMP. The overall structure belongs to the glycosyltransferase-B structural group. We could model a reasonable active conformation structure based on the crystal structure. The predicted structure suggested that the broad substrate specificity could be attributed to the wider entrance of the acceptor substrate binding site.     

Naturally-occurring tetrahydro-β-carboline alkaloids derived from tryptophan are oxidized to bioactive β-carboline alkaloids by heme peroxidases

β-Carbolines are indole alkaloids that occur in plants, foods, and endogenously in mammals and humans, and which exhibit potent biological, psychopharmacological and toxicological activities. They form from naturally-occurring tetrahydro-β-carboline alkaloids arising from tryptophan by still unknown way and mechanism. Results in this research show that heme peroxidases catalyzed the oxidation of tetrahydro-β-carbolines (i.e. 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid and 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid) into aromatic β-carbolines (i.e. norharman and harman, respectively). This oxidation followed a typical catalytic cycle of peroxidases through redox intermediates I, II, and ferric enzyme. Both, plant peroxidases (horseradish peroxidase, HRP) and mammalian peroxidases (myeloperoxidase, MPO and lactoperoxidase, LPO) catalyzed the oxidation in an efficient manner as determined by kinetic parameters (V_MAX and K_M). Oxidation of tetrahydro-β-carbolines was inhibited by peroxidase inhibitors such as sodium azide, ascorbic acid, hydroxylamine and excess of H₂O₂. The formation of aromatic β-carbolines by heme peroxidases can help to explain the presence and activity of these compounds in biological systems.     

Light Signal Transduction Pathway from Flavin Chromophore to the Jα Helix of Arabidopsis Phototropin1

In the plant blue-light sensor phototropin, illumination of the chromophoric LOV domains causes activation of the serine/threonine kinase domain. Flavin mononucleotide (FMN) is a chromophore molecule in the two LOV domains (LOV1 and LOV2), but only LOV2 is responsible for kinase activation. Previous studies reported an important role of an additional helix connected to the C-terminal of LOV2 (Jα helix) for the function of phototropin; however, it remains unclear how the Jα helix affects light-induced structural changes in LOV2. In this study we compared light-induced protein structural changes of the LOV2 domain of Arabidopsis phot1 in the absence (LOV2-core) and presence (LOV2-Jα) of the Jα helix by Fourier-transform infrared spectroscopy. Prominent peaks were observed only in the amide-I region (1650 (−)/1625 (+) cm⁻¹) of LOV2-Jα at physiological temperatures (≥260 K), corresponding to structural perturbation of the α-helix. The peaks were diminished by point mutation of functionally important amino acids such as Phe-556 between FMN and the β-sheet, Gln-575 being hydrogen-bonded with FMN, and Ile-608 on the Jα helix. We thus conclude that a light signal is relayed from FMN through these amino acids and eventually changes the interaction between LOV2-core and the Jα helix in Arabidopsis phot1.     

Biosynthesis of meteloidine from 3α-tigloyloxytropane in Datura innoxia

The administration of 3α-tigloyl-[1-¹⁴C]-oxytropane-[3β-³H] (³H/¹⁴C = 11·0 to Datura innoxia plants for 7 days led to the formation of radioactive meteloidine (³H/¹⁴C = 11·6). Degradation of the meteloidine indicated that the alkaloid was labeled specifically with ³H at C-3 of its teloidine moiety, and on the carbonyl group of its tigloyl residue with ¹⁴C. These results strongly favor the hypothesis that hydroxylation of tropine occurs after formation of its tigloyl ester.