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At least 19 recordsLinked to original sources
PubMed1978

Catabolite repression of isocitrate lyase in methylamine-grown Pseudomonas MA. Effect of carbon and nitrogen sources.

The synthesis of the C1-type isocitrate lyase found during growth of Pseudomonas MA on methylamine was investigated. It was shown that this enzyme is subject to catabolite repression by preferred carbon sources, e.g., succinate, and by ammonia. The carbon repression can be overcome by cyclic AMP, which was shown to be acting at the transcriptional level. Repression by ammonia is overcome during growth with methylamine as sole nitrogen, but not carbon, source. Uptake experiments showed that the uptake of methylamine from the medium was prevented by ammonia in the presence, but not in the absence, of an alternative carbon source. Measurement of cyclic AMP levels in cells grown on methylamine and on succinate, glycerol, glucose and acetate as carbon sources (with ammonium chloride as nitrogen source) revealed that methylamine-grown cells have the lowest cyclic AMP level despite having the highest C1-type isocitrate lyase activity. Cells grown on acetate with methylamine as sole nitrogen source possess both C1-type and C2-type isocitrate lyase. The results indicate that the synthesis of C1-isocitrate lyase is under control by repression-derepression involving a specific inducer, cyclic AMP, and an effector whose action is related to the nitrogen supply of the cell.

Ammonia↗
PubMed1978

Interactions of methylglyoxal with methylamine.

Ab initio quantum mechanical calculations are used to study the interactions of the aldehydic group of methylglyoxal with the NH2 groups of protein side-chains, using methylamine as a representative molecule. The hydrogen-bonding interaction, C = O...H - N, results in an electronic charge transfer from methylglyoxal to methylamine in both the ground and first excited triplet states. In this latter state a slight possibility is found for the H atom in the hydrogen bond to tunnel from methylglyoxal to methylamine, leading to the possible formation of two free radical fragments. The approach of methylamine to methylglyoxal in the stacked conformation C...N to form a hemiacetal, associated with electron charge transfer from methylamine to methylglyoxal, is energetically unfavourable in vacuum. The concomitant tunnelling of a proton from a proton-donating solvent molecule to the aldehydic oxygen of methylglyoxal is shown to make this approach favourable. The relative stability of the keto and enol forms of methylglyoxal is also investigated, the keto form being found the more stable in vacuum.

Aldehydes↗
PubMed1975

Methylamine and ammonia transport in Saccharomyces cerevisiae.

Methylamine (methylammonium ion) entered Saccharomyces cerevisiae X2180-A by means of a specific active transport system. Methylamine uptake was pH dependent (maximum rate between pH 6.0 and 6.5) and temperature dependent (increasing up to 35 C) and required the presence of a fermentable or oxidizable energy source in the growth medium. At 23 C the vmax for methylamine transport was similar 17 nmol/min per mg of cells (dry weight) and the apparent Km was 220 muM. The transport system exhibited maximal activity in ammonia-grown cells and was repressed 60 to 70 percent when glutamine or asparagine was added to the growth medium. There was no significant derepression of the transport system during nitrogen starvation. Ammonia (ammonium ion) was a strong competitive inhibitor of methylamine uptake, whereas other amines inhibited to a much lesser extent. Mutants selected on the basis of their reduced ability to transport methylamine (Mea-R) simultaneously exhibited a decreased ability to transport ammonia.

Amides↗
PubMed1978

Methylamine dehydrogenase of Pseudomonas sp. J. Purification and properties.

Methylamine dehydrogenase was purified in a homogeneous form from methylamine-grown Pseudomonas sp. J. The specific activity of the purified enzyme was 5.19 at 19 degrees C. The molecular weight was estimated to be 105 000, and the enzyme was composed of two kinds of subunit with molecular weights of 40 000 and 13 000, respectively. The enzyme contained little phosphorus, iron and copper. The enzyme had absorption maxima at 278, 330, 430 and 460 nm (shoulder). On addition of methylamine, the peaks at 430 and 460 nm decreased, while that at 330 nm increased. Primary amines served as substrates, but secondary and tertiary amines did not. Phenazine methosulfate was the most effective electron acceptor and oxygen was ineffective. The enzyme was inhibited by carbonyl reagents, cuprizone and HgCl2 but not by other chelators or sulfhydryl reagents. Some of other physical and biochemical properties of the enzyme were studied. These results show that the enzyme purified from Pseudomonas sp. J is essentially similar to the enzyme obtained from Pseudomonas AM1, although it differs slightly in some properties.

Amino Acids↗
PubMed1979

Faecal methylamine in normal and uraemic subjects.

1. A ninhydrin-reacting substance seen during ion-exchange chromatography of faecal dialysate obtained in vivo from normal and uraemic subjects has been isolated and identified as methylamine. 2. Faecal dialysate concentrations of methylamine were higher in uraemic subjects and were related to the degree of renal impairment (P less than 0.05). 3. Methylamine concentrations in faecal dialysate and centrifugate were not significantly different.

Centrifugation↗
PubMed1978

Methylamine dehydrogenase of Pseudomonas sp. J. Reconstitution from its subunits.

Conditions for the restoration of catalytic activity from heavy and light subunits which had been isolated from methylamine dehydrogenase of Pseudomonas sp. J were investigated in vitro. Maximal restoration of the activity was obtained in 0.8 M potassium phosphate buffer, pH 7.0-9.3, at 30 degrees C with equimolar concentrations of the two subunits. Under the optimal conditions, the recovery of enzyme activity was 86% and the time required for half-maximal recovery was about 3 min. Addition of bovine serum albumin or p-chloromercuribenzoate to the incubation mixture had no effect on the rate or extent of recovery of the enzyme activity. When the heavy subunit was added to the light subunit, the absorption spectrum of the light subunit changed to a form similar to that observed for the native enzyme. The concentration of methylamine required to change the spectrum of the light subunit was greatly decreased in the presence of the heavy subunit. Reconstituted enzyme was prepared from the isolated subunits and purified by gel chromatography. The reconstituted enzyme resembled the native enzyme in specific activity, molecular weight, substrate specificity, reaction mechanism, Michaelis constants for methylamine and phenazine methosulfate, susceptibility to inhibitor, and absorption, fluorescence and ESR spectra. However, it was less stable than the native enzyme to thermal and pH treatments. The CD spectrum was also slightly different from that of the native enzyme.

Circular Dichroism↗
PubMed1978

Methylamine dehydrogenases of Pseudomonas sp. J and Pseudomonas AM1. Study on subunit structure by dimethyl suberimidate.

Methylamine dehydrogenase (MW: 105,000) of Pseudomonas sp. J was treated with a bifunctional cross-linking reagent, dimethyl suberimidate. Cross-linked proteins having different molecular -eights of 53,000, 64,000, 80,000, 93,000, and 103,000 were found in addition to 13,000 (light subunit) and 40,000 (heavy subunit) by SDS polyacrylamide gel electrophoresis. Isolated light and heavy subunits were separately treated with the reagent. The product having a molecular weight of 80,000 was found to be a major cross-linked protein for the heavy subunit but no product was found for the light subunit. A similar electrophoretic pattern was also obtained for the reconstituted enzyme from the subunits of Pseudomonas sp. J and for methylamine dehydrogenase of Pseudomonas AM1. These results suggest that methylamine dehydrogenases obtained from these two bacteria are both the alpha2beta2-type subunit enzyme and have a geometrically analogous subunit structure.

Chemical Phenomena↗
PubMed1978

Methylamine dehydrogenase of Pseudomonase sp. J Isolation and properties of the subunits.

Two kinds of subunits, light subunit (Mr =1300) and heavy subunit (Mr=40 000), were isolated from a methylamine dehydrogenase (Mr=105 000) of Pseudomonas sp. J. The isolation of the subunits was carried out by gel chromatography after the enzyme had been treated with 3M guanidine-HCl. Coexistence of both of the subunit exhibited an absorption maximum only at 278 nm but in addition to the peak at 278 nm. The results indicate that the prosthetic group, assumed to be a derivative of pyridoxal, was bound to the light subunit. The spectral changes of the light subunit were observed by addition of methylamine. Various physical and biochemical parameters of the subunits are reported.

Amino Acids↗
PubMed1979

Counteraction of urea destabilization of protein structure by methylamine osmoregulatory compounds of elasmobranch fishes.

Intracellular fluids of marine elasmobranchs (sharks, skates and rays), holocephalans and the coelacanth contain urea at concentrations averaging 0.4m, high enough to significantly affect the structural and functional properties of many proteins. Also present in the cells of these fishes are a family of methylamine compounds, largely trimethylamine N-oxide with some betaine and sarcosine, and certain free amino acids, mainly beta-alanine and taurine, whose total concentration is approx. 0.2m. These methylamine compounds and amino acids have been found to be effective stabilizers of protein structure, and, at a 1:2 molar concentration ratio of these compounds to urea, perturbations of protein structure by urea are largely or fully offset. These counteracting effects of solutes on proteins are seen for: (1) thermal stability of protein secondary and tertiary structure (bovine ribonuclease); (2) the rate and extent of enzyme renaturation after acid denaturation (rabbit and shark lactate dehydrogenases); and (3) the reactivity of thiol groups of an enzyme (bovine glutamate dehydrogenase). Attaining osmotic equilibrium with seawater by these fishes has thus involved the selective accumulation of certain nitrogenous metabolites that individually have significant effects on protein structure, but that have virtually no net effects on proteins when these solutes are present at elasmobranch physiological concentrations. These experiments indicate that evolutionary changes in intracellular solute compositions as well as in protein amino acid sequences can have important roles in intracellular protein function.

4-Chloro-7-nitrobenzofurazan↗
PubMed1977

Methylamine dehydrogenase from the obligate methylotroph Methylomonas methylovora.

An obligate methyltroph Methylomonas methylovora oxidized methylamine, formaldehyde, and formate. Enzymes oxidizing these substrates were detected in a cell-free system. Phenazine methosulfate-linked methylamine dehydrogenase was purified 21-fold. The enzyme had optimum activity at pH 7.5 and was stable at 60 degrees C for 5 min. The enzyme activity was inhibited by parachloromercuric benzoate, isonicotinic acid hydrazide, mercuric chloride, and sodium borate.

Aldehyde Oxidoreductases↗
PubMedDate not supplied

[NAD-dependent N-methylglutamate dehydrogenase--new enzyme metabolizing methylamine in methylotrophs].

The properties of N-methylglutamate dehydrogenase, a new enzyme of methylamine metabolism in a facultative methylotroph Pseudomonas methylica, strain 2, were investigated. The enzyme was strictly dependent on the NAD presence and was not connected with particles in cell-free preparations. The enzyme appeared to be incucible and its activity increased after the growth of the cells in a medium containing methylamine.

Amino Acid Oxidoreductases↗
PubMed1978

Methylamine dehydrogenase of Pseudomonas AM1. A subunit enzyme.

A methylamine dehydrogenase was purified to homogeneity from Pseudomonas AM1 and obtained in crystalline form. It was found to be a subunit enzyme composed of two kinds of subunit, light and heavy. These two subunits were isolated by Sephadex G-100 gel chromatography after incubation of the enzyme with guanidine hydrochloride. Molecular weights of 13,000 daltons for the light subunit and 40,000 daltons for the heavy subunit were estimated by SDS-polyacrylamide gel electrophoresis, and the molecular weight of the native enzyme was found to be 105,000 daltons by Sephadex G-200 gel chromatography. The enzyme and its subunits were also analyzed for amino acid composition, isoelectric point, and absorption fluorescence, and CD spectra, as well as for the effects of pH, thermal treatment, and guanidine hydrochloride treatment. Both the subunits were absolutely required for enzymatic activity, either subunit alone being inactive. It could be deduced from the absorption and fluorescence spectra of the subunits that the prosthetic group of the enzyme was bound solely to the light subunit. These results suggest that the enzyme is a subunit enzyme similar to that of Pseudomonas sp. J, of the alpha2beta2 type.

Amino Acids↗
PubMed1979

In vitro metabolism of creatinine, methylamine and amino acids by intestinal contents of normal and uraemic subjects.

An original method which uses in vitro anaerobic incubation at 37 degrees C followed by centrifugation, ultrafiltration, and ion exchange chromatography is described; it shows that faecal material suspended in physiological saline can destroy added creatinine. The rate of breakdown by suspensions from uraemic subjects (mean 780 mumol h-1kg-1 SEM 70) was slightly faster than in normal subjects (mean 550 mumol h-1kg-1 SEM 80). Methylamine concentration increased over eight hours as creatinine was metabolised and sarcosine appeared as an intermediate. The rates of these reactions varied within and between individuals and were inhibited by oxygen and centrifugation but not by oxytetracycline. Concentrations of free amino acids did not change significantly despite the formation of ammonia. This approach should be useful in studying the metabolic inter-relationships between intestinal contents and the host organism in health and disease.

Adult↗
PubMed1976

Comparison of microelectrode, DMO, and methylamine methods for measuring intracellular pH.

The intracellular pH (pHi) of giant barnacle muscle fibers was measured with glass microelectrodes and also calculated from the distribution of 5,5-dimethyl-2,4-oxazolidinedione (DMO) and methylamine (MA). Simultaneously applying any two of these methods to muscle fibers of the same barnacle, we found the pH measured with an intracellular electrode (pH-Elec) to be about 0.06 higher than the DMO-derived pH (pH-DMO), and pH-DMO to be about 0.10 higher than the MA-derived pH (p-ma). in studies on the pHi of squid giant axons, we found that pH-Elec (7.35) and pH-DMO (7.36) were not significantly different. In the barnacle experiments, DMO required about 30 min to reach a steady-state distribution, while MA required more than 5 h. The deviations of pH-DMO and pH-MA from pH-Elec for the barnacle can be explained by a) an error in the assumed intracellular pKa' of DMO or MA, b) membrane permeability to the ionic form of DMO or MA, or c) intracellular compartmentalization. Included is a detailed study of the apparent dissociation constant of DMO as affected by temperature, and ionic strength and composition.

Animals↗
PubMed1979

Metabolism of isomeric N-methyl-N-nitroso-(methylphenyl)-methylamines.

Isomeric N-methyl-N-nitroso-(2-, 3-, and 4-methylphenyl)-methylamines (2a, 2b and 2c, Fig. 1.) were metabolized in rats to the corresponding 2-, 3- and 4-(N-methyl-N-nitroso-aminomethyl)-benzoic acids (4-MNAB) (3a, 3b and 3c). The structures of 3b and 2c were established by synthesis and confirmed by spectroscopic evidence. Metabolic formation of 3a, 3b and 3c was determined by HPLC analysis and the time-course of 3c excretion was established. Oral intubation of the acid 3c resulted in almost quantitative excretion of this metabolite in 24 h urine thus indicating rapid detoxication. Toxicity and carcinogenicity of the isomeric 2a, 2b and 2c were compared with those of the parent N-methyl-N-nitroso-benzylamine (MNBA).

Animals↗
PubMed1978

Characterization of DNA-protein cross-links formed by treatment of L1210 cells and nuclei with bis(2-chloroethyl)methylamine (nitrogen mustard).

Proteins cross-linked to DNA after nitrogen mustard (HN2) treatment of cells or isolated nuclei were purified in CsCl gradients. The protein-DNA cross-links could be cleaved by incubation in dilute acid and could be stabilized by alkali pretreatment. These results indicate that proteins cross-linked to DNA by HN2 are bound to alkylated purines. Analysis of the DNA-bound proteins on NaDodSO4-polyacrylamide gels showed that primarily large nonhistone proteins are cross-linked to DNA in cells treated with HN2. Very little if any histone is cross-linked to the DNA. Comparison of DNA bound proteins from HN2-treated cells and HN2-treated nuclei showed that in general the same proteins are linked to DNA in both cases, but some qualitative and quantitative differences exist.

Alkylation↗