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PubMed2005

Hansenula polymorpha NMR2 and NMR4, two new loci involved in nitrogen metabolite repression.

In the yeast Hansenula polymorpha (Pichia angusta) nitrate assimilation is tightly regulated and subject to a dual control: nitrogen metabolite repression (NMR), triggered by reduced nitrogen compounds, and induction, elicited by nitrate itself. In a previous paper [Serrani, F., Rossi, B. and Berardi, E (2001) Nitrogen metabolite repression in Hansenula polymorpha: the nmrl-l mutation. Curr. Genet. 40, 243-250], we identified five loci (NMR1-NMR5) involved in NMR, and characterised one of them (NMR1), which likely identifies a regulatory factor. Here, we describe two more mutants, namely nmr2-1 and nmr4-1. The first one possibly identifies a regulatory factor involved in nitrogen metabolite repression by various nitrogen sources alternative to ammonium. The second one, apparently involved in ammonium assimilation, probably has sensor functions.

Fungal Proteins↗
PubMed2006

Cyanobacterial response regulator PatA contains a conserved N-terminal domain (PATAN) with an alpha-helical insertion.

The cyanobacterium Anabaena (Nostoc) PCC 7120 responds to starvation for nitrogen compounds by differentiating approximately every 10th cell in the filament into nitrogen-fixing cells called heterocysts. Heterocyst formation is subject to complex regulation, which involves an unusual response regulator PatA that contains a CheY-like phosphoacceptor (receiver, REC) domain at its C-terminus. PatA-like response regulators are widespread in cyanobacteria; one of them regulates phototaxis in Synechocystis PCC 6803. Sequence analysis of PatA revealed, in addition to the REC domain, a previously undetected, conserved domain, which we named PATAN (after PatA N-terminus), and a potential helix-turn-helix (HTH) domain. PATAN domains are encoded in a variety of environmental bacteria and archaea, often in several copies per genome, and are typically associated with REC, Roadblock and other signal transduction domains, or with DNA-binding HTH domains. Many PATAN domains contain insertions of a small additional domain, termed alpha-clip, which is predicted to form a four-helix bundle. PATAN domains appear to participate in protein-protein interactions that regulate gliding motility and processes of cell development and differentiation in cyanobacteria and some proteobacteria, such as Myxococcus xanthus and Geobacter sulfurreducens.

Amino Acid Sequence↗
PubMed1992

Differentially regulated malate synthase genes participate in carbon and nitrogen metabolism of S. cerevisiae.

We have isolated a second gene (MLS1), which in addition to DAL7, encodes malate synthase from S. cerevisiae. Expression of the two genes is specific for their physiological roles in carbon and nitrogen metabolism. Expression of MLS1, which participates in the utilization of non-fermentable carbon sources, is sensitive to carbon catabolite repression, but nearly insensitive to nitrogen catabolite repression. DAL7, which participates in catabolism of the nitrogenous compound allantoin, is insensitive to carbon catabolite repression, but highly sensitive to nitrogen catabolite repression. Results obtained with null mutations in these genes suggest that S. cerevisiae contains at least one and perhaps two additional malate synthase genes.

Amidine-Lyases↗
PubMed1997

Nitroarenes of photochemical origin: a possible source of risk to human health.

Nitrated polynuclear aromatics (NPAH) have been recognized as mutagenic even without enzymatic activation. NPAH have been found in the urban air of the U.S.A. and Western Europe. Their detection in the atmosphere has been related mainly to in situ photochemical production. In this study, the ubiquity of NPAH in the air is presented despite their rare and scarce occurrence in emissions released by mobile and stationary sources. NPAH seem to effectively contribute to both the direct and indirect mutagenicity of air soot (in European countries more than in the U.S.A.). Moreover, they can be taken as a suitable index of the occurrence of reactive nitrogen compounds in the air.

Gas Chromatography-Mass Spectrometry↗
PubMed1980

The biochemistry and technology of tea manufacture.

This review surveys tea-production technology, chemistry of raw and manufactured tea as well as tea tasting appraisal and chemical analysis of manufactured tea. The paper describes the healthful properties of tea, gives general information on the tea plant and manufactured tea, and presents classification of teas as related to the processing of black green, yellow, and red tea, green pressed tea as well as instant tea and tea dyes. The paper discusses the chemical composition of raw and manufactured tea as well as approaches to the evaluation of tea quality--tea tasting appraisal and chemical analysis. The paper is supplied with the conclusions and references. The section on the healthful properties of tea discusses various aspects of catechin effects--vitamin P, antimicrobial, antioxidative and radioprotective effects. Also described are favorable effects of tea alkaloids--caffeine, theobromine, theophylline that dilatate cerebral vessels and alleviate headaches. The section on the production of different teas (black, green, yellow, red, instant teas, and tea dyes) considers technological methods and biochemical bases of various types of tea manufacture. The role of tea leaf enzymes in the oxidative processes determining the tea quality is discussed in detail. This section also describes the contribution of thermochemical processes into the formation of tea flavor. The compounds dictating tea taste and aroma are discussed, particularly tannins and catechins, volatile oils, nitrogen compounds, and some other substances.

Alkaloids↗
PubMed1993

[Nitrates and nitrites in gastric juice in chronic gastritis].

Atrophic gastritis is precancerous condition of the intestinal type of gastric carcinoma. This process supposes a genotoxic effect of N-nitroso-compounds which are formed in the stomach by nitrosation of nitrites and organic nitrogen compounds. The authors examined 41 patients with chronic superficial and atrophic gastritis. They examined the pH and concentration of nitrates and nitrites in gastric juice taken in the morning before meal. They discovered that in severe atrophic gastritis the amount of nitrates is significantly increased and the amount of nitrites is decreased, all in comparison with superficial gastritis. An exponential relation of the concentration of nitrites towards the pH of gastric juice was found to be NO2- = epH-6.5, CC = 0.935. A significant elevation of nitrite concentration was observed in cases of pH being higher than 5.5. Nitrate concentration altered in dependence of the value of gastric pH. Oral administration of 300 mg of vitamin C or 250 mg of vitamin E did not significantly affect the amount of gastric nitrites. The work discusses the mutual relation of nitrites, ascorbic acid and alpha-tocopherol towards the formation of N-nitroso-compounds in the stomach inflicted by atrophic gastritis. (Tab. 3, Fig. 2, Ref. 25.)

Adult↗
PubMed2004

The Pseudomonas putida Crc global regulator controls the expression of genes from several chromosomal catabolic pathways for aromatic compounds.

The Crc protein is involved in the repression of several catabolic pathways for the assimilation of some sugars, nitrogenated compounds, and hydrocarbons in Pseudomonas putida and Pseudomonas aeruginosa when other preferred carbon sources are present in the culture medium (catabolic repression). Crc appears to be a component of a signal transduction pathway modulating carbon metabolism in pseudomonads, although its mode of action is unknown. To better understand the role of Crc, the proteome profile of two otherwise isogenic P. putida strains containing either a wild-type or an inactivated crc allele was compared. The results showed that Crc is involved in the catabolic repression of the hpd and hmgA genes from the homogentisate pathway, one of the central catabolic pathways for aromatic compounds that is used to assimilate intermediates derived from the oxidation of phenylalanine, tyrosine, and several aromatic hydrocarbons. This led us to analyze whether Crc also regulates the expression of the other central catabolic pathways for aromatic compounds present in P. putida. It was found that genes required to assimilate benzoate through the catechol pathway (benA and catBCA) and 4-OH-benzoate through the protocatechuate pathway (pobA and pcaHG) are also negatively modulated by Crc. However, the pathway for phenylacetate appeared to be unaffected by Crc. These results expand the influence of Crc to pathways used to assimilate several aromatic compounds, which highlights its importance as a master regulator of carbon metabolism in P. putida.

Bacterial Proteins↗
PubMed1998

Physiology of organic nitrogen acquisition by ectomycorrhizal fungi and ectomycorrhizas.

Ectomycorrhizal fungi are symbiotically associated microorganisms which ecological importance has been repeatedly demonstrated. There has been a considerable amount of research aimed at assessing the ability of ectomycorrhizal fungi and ectomycorrhizas to utilize organic nitrogen sources. The fate of soil proteins, peptides and amino acids has been studied from a number of perspectives. Exocellular hydrolytic enzymes have been detected and characterized in a number of ectomycorrhizal and ericoid fungi. Studies on amino acid transport through the plasma membrane have demonstrated the ability of ectomycorrhizal fungi to take up the products of proteolytic activities. Investigations on intracellular metabolism of amino acids have allowed the identification of the metabolic pathways involved. Possible intracellular compartmentation of amino acids will be examined by immunocytochemistry. Further translocation of amino acids in symbiotic tissues has been established by experiments using isotopic tracers, although the exact nature of the nitrogenous compounds transferred at the symbiotic interface remained unclear. One of the main future challenges in the physiology of organic nitrogen acquisition is to determine the nature, the regulation and the location of N-compound transporters at the soil-fungus and fungus-plant interfaces. The molecular approach which is just emerging in this particular research area will greatly improve our knowledge. Future research should also address the extent of competition between different ectomycorrhizal species and between different microbial populations for organic nitrogen.

Amino Acids↗
PubMed1984

Binding of ligands to the catalytic zinc ion in horse liver alcohol dehydrogenase.

The affinity of nitrogen and sulfur ligands for the catalytic zinc ion in horse liver alcohol dehydrogenase has been investigated by their influence on the affinity labeling reaction with iodoacetate. All the nitrogen compounds including ammonia, a primary and a secondary amine, and heterocycles containing a pyridine-type nitrogen with the exception of 2,2-dipyridyl were found to activate the affinity labeling reaction. Activation results from inner-sphere ligand coordination to the catalytic zinc ion. Closely related pyridine compounds gave a regular increase in affinity for the enzyme with increasing basicity, as expected for coordination to a metal ion. The sulfur compounds penicillamine and mercaptoethanol also activated the affinity labeling reaction, but dimercaptopropanol bound very tightly as a bidentate inhibited the reaction. The anions hydrosulfide, diethyldithiocarbamate, and cyanide coordinated to the catalytic zinc ion, whereas azide, thiocyanate, tetrazole, and iodide complexed the anion-binding site. The anionic metal ligands increased the rate of inactivation of the enzyme with iodoacetamide by binding to the catalytic zinc ion, while the binding of iodoacetate to the anion-binding site was prevented.

2,2'-Dipyridyl↗
PubMed2005

Optimization of the aerobic biological treatment of thermophilically treated refractory wastewater.

A pilot scale conventional activated sludge was operated for over 600 days to study its effectiveness at further remediating the effluent of an existing industrial site's thermophilic biological treatment stage. During the course of the study, the activated sludge was able to further biodegrade the contaminants in the incoming industrial wastewater in terms of both BOD and nitrogen reductions at varying hydraulic and solids retention times, despite elevated concentrations of soluble copper being present. A limiting hydraulic retention time (HRT) for BOD removal of 1.5 days was observed as well as the loss of nitrification occurred at a solids retention time (SRT) of approximately 6 days. Biokinetic coefficients were determined with the maximum rate of substrate utilization per unit mass of microorganisms, k, of 0.14 mgVSS/(mgsBOD-d) and the Monod half velocity constant, K(s), of 9.4 mgsBOD/L. Simultaneous nitrification and denitrification (SND) of the nitrogenous compounds found in this wastewater was observed throughout the majority of the experimentation while the bulk DO in the system was greater than 1 mg/L. The activated sludge was estimated to contain soluble copper on the order of 1 mg/L throughout the course of operation with no apparent detriment to nitrification. Additionally, the activated sludge was able to biologically remove the main solvents found in the influent wastewater. The removals of trace levels of N-nitrosodimethylamine (NDMA) were also observed.

Biodegradation, Environmental↗
PubMed1983

Nitrogen Turnover and Assimilation during Regrowth in Trifolium subterraneum L. and Bromus mollis L.

Subterranean clover (Trifolium subterraneum L. cv Woogenellup) and soft chess grass (Bromus mollis L. cv Blando) were grown in monocultures with (15)NH(4)Cl added to the soil to study nitrogen movement during regrowth following shoot removal. Four clipping treatments were imposed. Essentially all available (15)N was assimilated from the soil prior to the first shoot harvest. Measurements of total reduced nitrogen and (15)N contained within that nitrogen fraction in roots, crowns, and shoots at each harvest showed large, significant (P </= 0.001) declines in excess (15)N of crowns and roots in both species between the first and fourth harvests. There was no significant decline in total reduced nitrogen in the same organs over that period. Similar responses were evident in plants defoliated three times. The simplest interpretation of these data is that reduced nitrogen compounds turn over in plant roots and crowns during shoot regrowth. Calculations for grass and clover plants clipped four times during the growing season indicated that 100 to 143% of the nitrogen present in crowns and roots turned over between the first and fourth shoot harvest in both species, assuming nitrogen in those organs was replaced with nitrogen containing the lowest available concentration of (15)N. If other potential sources of nitrogen were used for the calculations, it was necessary to postulate that larger amounts of total nitrogen flowed through the crown and root to produce the measured dilution of (15)N compounds. These data provide the first quantitative estimates of the amount of internal nitrogen used by plants, in addition to soil nitrogen or N(2), to regenerate shoots after defoliation.

Journal Article↗
PubMed2006

Enantiomeric purity methods for three pharmaceutical compounds by electrokinetic capillary chromatography utilizing highly sulfated-gamma-cyclodextrin as the chiral selector.

Methods for enantiomeric purity by electrokinetic chromatography were developed and validated for three pharmaceutical compounds, each utilizing highly sulfated-gamma-cyclodextrin (HS-gamma-CD) as the chiral recognition agent. Two of the compounds are weak bases, hence charged at low pH, and the third is a quaternary nitrogen compound, charged at all pH. In each instance quantification was via an authentic reference standard with addition of an internal standard. Separation was on a 61 cm x 50 microm untreated capillary under reverse polarity with a background electrolyte of 5% HS-gamma-CD in pH 2.50 lithium phosphate buffer. Each method was validated with respect to the usual validation parameters, notably recovery and precision, yielding results, including limits of detection and quantitation, that allow reporting the minor enantiomer to 0.1% and less. In applying the methods, all batches of bulk drug tested were shown to be of enantiomeric purity > or =99.9%.

Aza Compounds↗
PubMed1983

Identification of the metabolites of benzo[f]quinoline and benzo[h]quinoline formed by rat liver homogenate.

Benzo[f]quinoline and benzo[h]quinoline are widespread environmental pollutants which have been found to be mutagenic. The metabolism of benzo[f]quinoline and benzo[h]quinoline was investigated using a liver homogenate from Aroclor-pretreated rats. The metabolites of benzo[f]quinoline which were identified were 7,8-dihydroxy-7,8-dihydrobenzo[f]quinoline, 9,10-dihydroxy-9,10-dihydrobenzo[f]quinoline, 7-hydroxybenzo[f]quinoline, and benzo[f]quinoline-N-oxide. Metabolism studies on benzo[f]quinoline performed in the presence of the epoxide hydratase inhibitor, 3,3,3-trichloropropylene oxide, demonstrated that the formation of both of these dihydrodiols can be inhibited. The major metabolites of benzo[h]quinoline were identified as 5,6-dihydroxy-5,6-dihydrobenzo[h]quinoline and 7,8-dihydroxy-7,8-dihydrobenzo[h]quinoline. Benzo[h]quinoline-N-oxide was not detected as a metabolite. In the presence of an epoxide hydratase inhibitor, the major metabolites of benzo[h]quinoline were 5,6-epoxybenzo[h]quinoline and 7-hydroxybenzo[h]quinoline. The difference in the metabolism to N-oxides observed between benzo[h]quinoline and benzo[f]quinoline is consistent with previous observations in which sterically hindered aromatic ring nitrogen compounds such as benzo[h]quinoline are more resistant to N-oxide formation. The nitrogen atom of these aza-arenes with its lone pair of electrons has a significant influence on sites at which dihydrodiols are formed. The data suggest that the aromatic ring nitrogen of these azaphenanthrenes has an effect similar to that of a methyl substituent in directing their metabolic oxidation.

Animals↗
PubMed2004

Understanding odorants associated with compost, biomass facilities, and the land application of biosolids.

Odorous water and air can result from compost, biomass facilities and land application of biosolids. Common odorous compounds from these biodegradation systems include alcohols, aldehydes, fatty acids, solvents and various sulfur and nitrogen compounds. Each odorant possesses a unique individual odor signature i.e. odor character or quality, odor threshold concentration and chemical concentration. This paper develops an initial understanding of how the volatile odorous chemicals and their relative concentrations produced are related to the total odor quality from the process by their odor threshold concentrations. The compost process is used as an example. It was estimated, that on day 1 and 7, the primary fatty acids controlling the fermented and rotten odors were butyric acid and valeric acids, individually, unpleasant and rancid odors, respectively, although acetic acid had the highest fatty acid concentration on both days. In the same way, aldehydes and ketones controlled the disappearance of the sweet odor from day 1 to 7.

Acids↗
PubMed2004

Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico.

The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident.

Chromatography, Gas↗