Biomedical subjects

G D Vogels

Publications and source records attributed to G D Vogels.

At least 55 records · Page 3Linked to original sources

PubMed1991

Methanogenic pathways in Methanosphaera stadtmanae.

Methanosphaera stadtmanae reduces methanol to CH4 in a similar way as Methanosarcina barkeri. Low activities of 5,10-methylenetetrahydromethanopterin dehydrogenase (MTDH) and reductase (MTR) were found. From studies on formaldehyde oxidation and reduction it was concluded that most likely the inability to reduce CO2 to CH4 was due to the lack of an active or the presence of an inactive CO2 reductase system and methyltetrahydromethanopterin (methyl-H4MPT): coenzyme M methyltransferase. Methanofuran was not detected, while the presence of a pterin, analogous to H4MPT, could be substantiated from its degradation products in boiled extracts.

Carbon Dioxide↗

PubMed1991

In vitro inhibition of cell growth of MOLT-4 malignant human T-lymphoblasts by coenzyme F420.

The inhibitory effect of methanogenic coenzymes on the proliferation of MOLT-4 human malignant T-lymphoblasts was tested. Furthermore the effects of methanogenic coenzymes on dihydrofolate reductase activity (DHFR) from chicken liver have been examined. The results showed that heat-stable extracts of the hydrogenotrophs Methanobacterium thermoautotrophicum, Methanoculleus thermophilicum and Methanogenium tationis inhibit both proliferation of human T-lymphoblasts and DHFR activity. Heat-stable extract of the methylotroph Methanosarcina barkeri showed neither inhibitory nor stimulatory effects in both test systems. The present study proves coenzyme F420 to be the active, inhibitory component in methanogenic extracts.

Cell Division↗

PubMed1991

Purification and characterization of coenzyme F420-dependent 5,10-methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum strain delta H.

5,10-Methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum strain delta H was purified to homogeneity with nearly complete recovery. The aerobically stable monofunctional enzyme catalyzed the reversible oxidation of 5,10-methylene-5,6,7,8-tetrahydromethanopterin to its 5,10-methenyl derivative. For the reaction a midpoint potential E'0 = - 362 mV was calculated at 60 degrees C. The methanogenic electron carrier coenzyme F420 was strictly required as the co-substrate. The dehydrogenase (Mr 216,000) was purified as an apparent hexamer of six identical 36 kDa subunits. Oxidation of 5,10-methylenetetrahydromethanopterin coupled to coenzyme F420 reduction catalyzed by the dehydrogenase with a turnover number of 2400 S-1 proceeded via a ternary complex mechanism. High concentrations of monovalent cations markedly stimulated the reaction.

Euryarchaeota↗

PubMed1991

Fermentation of cellulose and production of cellulolytic and xylanolytic enzymes by anaerobic fungi from ruminant and non-ruminant herbivores.

Four anaerobic fungi were grown on filter paper cellulose and monitored over a 7-8 days period for substrate utilisation, fermentation products, and secretion of cellulolytic and xylanolytic enzymes. Two of the fungi (N1 and N2) were Neocallimastix species isolated from a ruminant (sheep) and the other two fungi were Piromyces species (E2 and R1) isolated from an Indian Elephant and an Indian Rhinoceros, respectively. The tested anaerobic fungi degraded the filter paper cellulose almost completely and estimated cellulose digestion rates were 0.25, 0.13, 0.21 and 0.18 g.l-1.h-1 for strains E2, N1, N2, R1, respectively. All strains secreted cellulolytic and xylanolytic enzymes, including endoglucanase, exoglucanase, beta-glucosidase and xylanase. Strain E2 secreted the highest levels of enzymes in a relatively short time. The product formation on avicel by enzymes secreted by the four fungi was studied. Both in the presence and absence of glucurono-1,5-delta-lactone, a specific inhibitor of beta-glucosidase, mainly glucose was formed but no cellobiose. Therefore the exoglucanase secreted by the four fungi is probably a glucohydrolase.

Anaerobiosis↗

PubMed1991

Ammonia assimilation and glutamate incorporation in coenzyme F420 derivatives of Methanosarcina barkeri.

Methanosarcina barkeri was able to grow on L-alanine and L-glutamate as sole nitrogen sources. Cell yields were 0.5 g/l and 0.7 g/l (wet wt), respectively. The mechanism of ammonia assimilation in Methanosarcina barkeri strain MS was studied by analysis of enzyme activities. Activity levels of nitrogen-assimilating enzymes in extracts of cells grown on different nitrogen sources (ammonia, 0.05-100 mM; L-alanine, 10 mM; L-glutamate, 10 mM) were compared. Activities of glutamate dehydrogenase, glutamate synthase, glutamine synthetase, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase could be measured in cells grown on these three nitrogen sources. Alanine dehydrogenase was not detected under the growth conditions used. None of the measured enzyme activities varied significantly in response to the NH4+ concentration. The length of the poly-gamma-glutamyl side chain of F420 derivatives turned out to be independent of the concentration of ammonia in the culture medium.

Alanine↗

PubMed1991

Comparison of growth characteristics of anaerobic fungi isolated from ruminant and non-ruminant herbivores during cultivation in a defined medium.

Anaerobic fungi were isolated from rumen fluid of a domestic sheep (Ovis aries; a ruminant) and from faeces of five non-ruminants: African elephant (Loxodonta africana), black rhinoceros (Diceros bicornis), Indian rhinoceros (Rhinoceros unicornis), Indian elephant (Elephas maximus) and mara (Dolichotis patagonum). The anaerobic fungus isolated from the sheep was a Neocallimastix species and the isolates from non-ruminants were all species similar to Piromyces spp. A defined medium is described which supported growth of all the isolates, and was used to examine growth characteristics of the different strains. For each fungus the lipid phosphate content was determined after growth on cellobiose and the resulting values were used to estimate fungal biomass after growth on solid substrates. The ability of isolates from ruminants and non-ruminants to digest both wheat straw and cellulose was comparable. More than 90% and 60%, respectively, of filter paper cellulose and wheat straw were digested by most strains within 60-78 h. Growth of two fungi, isolated from rumen fluid of a sheep (Neocallimastix strain N1) and from faeces of an Indian rhinoceros (Piromyces strain R1), on cellobiose was studied in detail. Fungal growth yields on cellobiose were 64.1 g (mol substrate)-1 for N1 and 34.2 g mol-1 for R1. The major fermentation products of both strains were formate, lactate, acetate, ethanol and hydrogen.

Anaerobiosis↗

PubMed1991

Evolution of Volatile Sulfur Compounds during Laboratory-Scale Incubations and Indoor Preparation of Compost Used as a Substrate in Mushroom Cultivation.

Volatile sulfur compounds are known to be produced during the preparation of compost used as a substrate in mushroom cultivation. Because they cause odor problems, attempts have been made to reduce the production of these compounds. The influences of temperature and various additions on the production of volatile sulfur compounds from composting material were tested on laboratory-scale preparations. The production of H(2)S, COS, CH(3)SH, and (CH(3))(2)S was proven to be a biological process with an optimal temperature that coincides with the optimal temperature for biological activity. The formation of CS(2) and (CH(3))(2)S(2) was shown to be a nonbiological process. The emission of volatile sulfur compounds during the indoor preparation of mushroom compost appeared to be remarkably reduced (about 90%) as compared with the emission during the conventional outdoor process. Introduction of this indoor composting process would result in a significant reduction in environmental pollution.

Journal Article↗

PubMed1991

Identification of para-Cresol as a Growth Factor for Methanoplanus endosymbiosus.

Growth of the methanogenic bacterium Methanoplanus endosymbiosus is dependent on the presence of ruminal fluid. Ruminal fluid could be replaced by the eluate of a rumen-derived anaerobic digester. From the eluate of the digester, a growth-stimulatory component was purified and identified as p-cresol. Authentic p-cresol supported a half-maximal growth rate of the organism at 50 nM concentration.

Journal Article↗

PubMed1991

Hydrolysis and reduction of factor 390 by cell extracts of Methanobacterium thermoautotrophicum (strain delta H).

Cell extracts of Methanobacterium thermoautotrophicum (strain delta H) were found to perform a hydrogen-dependent reduction of factor 390 (F390), the 8-adenylyl derivative of coenzyme F420. Upon resolution of cell extracts, F390-reducing activity copurified with the coenzyme F420-dependent hydrogenase. This indicates that F390 serves as a substrate of that enzyme. Activity towards F390 was approximately 40-fold lower than that towards coenzyme F420 (0.12 and 5.2 mumol.min-1.mg of protein-1, respectively). In addition, cell extracts catalyzed the hydrolysis of F390 to AMP and coenzyme F420. This hydrolysis required the presence of thiols (6 mM) and much ionic strength (1 M KCl) and was reversibly inhibited by oxygen. The reaction proceeded optimally at pH 8.2 and was Mn dependent. Conditions for F390 hydrolysis in cell extracts are in many respects opposite to those previously described for F390 synthesis.

Adenosine Monophosphate↗

PubMed1991

F390 synthetase and F390 hydrolase from Methanobacterium thermoautotrophicum (strain delta H).

Factor F390 is the 8-OH adenylated form of the deazaflavin coenzyme F420, which is a central electron carrier in methanogenic bacteria. The enzymes catalysing the formation of F390 from ATP and F420 (F390 synthetase) and its hydrolysis into AMP and F420 (F390 hydrolase) were isolated and partially purified from Methanobacterium thermoautotrophicum. Both enzymes were oxygen-stable. The F390 synthetase tended to coelute with coenzyme F420 reducing hydrogenase during all purification steps. The 30-fold purified enzyme was still contaminated with the hydrogenase. The F390 hydrolase was purified 135-fold to a specific activity of 8.6 mumol/min/mg protein. The colourless enzyme consisted of one polypeptide of approximately 27,000 kd.

Electrophoresis, Polyacrylamide Gel↗

PubMed1991

Identification of a novel tatiopterin derivative in Methanogenium tationis.

Recently, a novel pterin has been isolated from Methanogenium tationis. This pterin derivative, which was called tatiopterin, was characterized as a methanopterin-like structure with an additional aspartyl and glutamyl group in the side chain and with a 7-proton instead of a 7-methyl group in the pterin moiety. The sequence of the aspartyl and glutamyl group remained unsolved. In this study, a novel pterin was purified from Mg.tationis and analyzed by 600 MHz 1H-NMR spectroscopy and fast atom bombardment-mass spectroscopy. This pterin was found to be an aspartyl derivative of methanopterin with a 7-proton in the pterin part of the molecule. No glutamyl group could be detected. Apparently, Mg.tationis is able to synthesize two types of tatiopterin derivatives. For these cofactors the trivial names 'tatiopterin-0' (lacking a glutamyl group) and 'tatiopterin-I' (containing one glutamyl group) are introduced here.

Amino Acids↗

PubMed1990

Purification and properties of 5,10-methylenetetrahydromethanopterin reductase, a coenzyme F420-dependent enzyme, from Methanobacterium thermoautotrophicum strain delta H.

5,10-Methylenetetrahydromethanopterin reductase was purified 22-fold to apparent homogeneity from the methanogenic bacterium Methanobacterium thermoautotrophicum. The enzyme catalyzes the reduction of 5,10-methylene- to 5-methyltetrahydromethanopterin. The electron carrier coenzyme F420 is specifically used as the cosubstrate. The reductase reaction may proceed in both directions, methylene reduction is, however, thermodynamically favored. In addition, the velocity of the reaction in this direction exceeds the reverse reaction by a factor of 26. The reductase is composed of a single subunit with an estimated Mr = 35,000. The active enzyme does not contain a flavin prosthetic group or iron-sulfur clusters, in contrast to 5,10-methylenetetrahydrofolate reductases purified from eukaryotic and eubacterial sources, which catalyze an analogous reaction as the methanogenic reductase.

Chromatography, Ion Exchange↗

PubMed1990

Effect of fixation on activity and cytochemistry of hydrogenosomal enzymes in Trichomonas vaginalis.

The effect of fixation on the activity of malate dehydrogenase (decarboxylating) and pyruvate synthase was investigated in Trichomonas vaginalis. Subsequently a cytochemical staining method was developed for the demonstration of malate dehydrogenase activity in hydrogenosomes. After fixation of cells in low concentrations of glutaraldehyde and incubation in the presence of malate and the tetrazolium compound 2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl)tetrazolium chloride, an electron-dense deposit was produced in the hydrogenosomes. During the whole procedure strictly anaerobic conditions were required. Attempts to develop an analogous procedure for pyruvate synthase failed because even low concentrations of glutaraldehyde strongly inhibited enzyme activity. When cells were fixed in low concentrations of glycolaldehyde and acetaldehyde, a high enzyme activity was retained, but no staining could be achieved. Application of both staining methods to the sapropelic ciliates Trimyema compressum and Plagiopyla nasuta gave negative results.

Animals↗

PubMed1990

Odorous Sulfur Compounds Emitted during Production of Compost Used as a Substrate in Mushroom Cultivation.

Large-scale composting facilities are known to cause environmental problems, mainly through pungent air emitted by composting material. In air samples taken above stacks set up to prepare compost used as a substrate in mushroom cultivation, several volatile compounds were identified by means of the coupled techniques of gas chromatography and mass spectrography. Among the compounds identified, sulfur-containing compounds [H(2)S, COS, CH(3)SH, CS(2), (CH(3))(2)S, (CH(3))(2)S(2), and (CH(3))(2)S(3)] are the most conspicuous in causing a nuisance. Quantification of these compounds was performed by concentrating a relatively small air sample on Tenax GC. The sampling method appeared to be very useful under field conditions. During the composting process, the concentration of the volatile sulfur compounds in emitted air ranged from 1 to 35 mumol/m. The highest concentrations were obtained at the end of the outdoor process. Total sulfur emission amounted to 8.3 mg of sulfur per kg (fresh weight) of compost. The end product still contained 2.58 g of sulfur per kg (fresh weight) of compost. Suggestions about the origin of the volatile sulfur compounds are made.

Journal Article↗

PubMed1990

Biomass and Biological Activity during the Production of Compost Used as a Substrate in Mushroom Cultivation.

The production of a suitable substrate for the cultivation of the common white button mushroom, Agaricus bisporus, is referred to as composting. High microbiological activity causes temperatures of the composting material to rise as high as 80 degrees C. At stacking, an optimal oxygen consumption rate of 140 mumol of O(2) h g (dry weight) was found in the compost at 50 degrees C, whereas the oxygen consumption rate of the end product was lower at all temperatures tested. No significant differences were observed between biomass content and mineralization rate of C-labeled glutamate of the two composts. Biomass content was shown to be a major function of both temperature and the sampling site position in the stack. On the basis of the results reported here, a minimal composting time of 3.3 days for the phase I process was calculated. Further suggestions are made to reduce the time necessary for the production of a substrate for A. bisporus considerably.

Journal Article↗

PubMed1990

Methanogenesis involving a novel carrier of C1 compounds in Methanogenium tationis.

The pathway of CO2 reduction to methane in Methanogenium tationis and Methanogenium thermophilicum is similar to that observed in other methanogens. In M. tationis a novel pterin, tatiopterin, is present. This pterin appears to be a structural and functional analog of methanopterin and sarcinapterin. Folate could not substitute for tatiopterin.

Carbon Dioxide↗

PubMed1990

Purification and properties of 5,10-methenyltetrahydromethanopterin cyclohydrolase from Methanosarcina barkeri.

The 5,10-methenyltetrahydromethanopterin cyclohydrolase from Methanosarcina barkeri was purified 313-fold to a specific activity of 470 mumol min-1 mg-1 at 37 degrees C and pH 7.8. At this stage, the enzyme was pure as judged from polyacrylamide gel electrophoresis. The monofunctional enzyme was oxygen stable, but the presence of a detergent proved to be essential for its stability. Like the cyclohydrolase purified from Methanobacterium thermoautotrophicum (A. A. Dimarco, M. I. Donnelly, and R. S. Wolfe, J. Bacteriol. 168:1372-1377, 1986), the protein showed an apparent Mr of 82,000, and it is composed of two identical subunits as was concluded from nondenaturating and denaturating polyacrylamide gel electrophoresis. The enzymes from M. thermoautotrophicum and M. barkeri markedly differ with respect to the hydrolysis product of 5,10-methenyltetrahydromethanopterin: 5-formyl- and 10-formyltetrahydromethanopterin, respectively. The apparent Km for 5,10-methenyltetrahydromethanopterin was 0.57 mM at 37 degrees C and pH 7.8.

Aminohydrolases↗

PubMed1989

Stimulation of the methylcoenzyme M reduction by uridine-5'-diphospho-sugars in cell-free extracts of Methanobacterium thermoautotrophicum (strain delta H).

The hydrogen-dependent reduction of methylcoenzyme M catalyzed by coenzyme-depleted cell-free extracts of Methanobacterium thermoautotrophicum was stimulated by micromolar concentrations of a UDP-disaccharide present in the organism. The compound was isolated and identified as UDP-1-O-alpha-D-2-acetamido-2-deoxyglucopyranose (UDPGlcpNAc) glycosidically linked to 2-acetamido-2-deoxymannopyranosyluronic acid. Maximal stimulation was observed when both the UDP-disaccharide and mercaptoheptanoylthreonine phosphate were present in the reaction mixtures. The UDP derivative isolated was not specific in its action: other UDP-sugars tested in micromolar concentrations stimulated the methylcoenzyme M reduction to the same extent. The activated sugars presumably substitute for ATP, which is usually required in much higher concentrations to activate the methylcoenzyme M reductase system.

Adenosine Triphosphate↗