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PubMed1992

Effects of chloroquine and methylamine on lysosomal enzyme secretion by rat pancreas.

In vivo pancreatic secretion of the lysosomal hydrolase cathepsin B was found to be increased by infusion of the secretagogue caerulein. The basal as well as caerulein-stimulated in vivo rate of cathepsin B was further increased by infusion of either chloroquine or methylamine while neither the basal nor the secretagogue-stimulated rates of amylase secretion were altered by the lysosomotropic agents. These observations indicate that neutralization of the acidic prelysosomal compartment by administration of lysosomotropic agents results in lysosomal enzyme entry, by default, into the regulated secretory pathway. In vitro stimulation of pancreatic acini with caerulein was also found to stimulate cathepsin B secretion. That in vitro rate of cathepsin B secretion stimulated by caerulein was not increased in acini prepared from animals infused with caerulein, chloroquine, or methylamine, but the in vitro rate of cathepsin B secretion stimulated by caerulein was increased in acini prepared from animals infused with caerulein plus either chloroquine or methylamine. Under these conditions, redistribution of cathepsin B from the lysosome-enriched to the zymogen granule-enriched subcellular fraction was noted, and lysosomal enzyme-containing organelles became increasingly fragile. These observations indicate that in vivo secretagogue stimulation increases the degree of diversion of lysosomal hydrolases into the regulated secretory compartment when the prelysosomal compartment has been neutralized with lysosomotropic agents.

Amylases↗
PubMed1989

Methylamine and polyol responses to salt loading in renal inner medulla.

Methylamines and polyhydric alcohols (polyols) are major organic osmolytes of the mammalian renal inner medulla and have generally been noted to change in parallel with urine osmolality. In the present study, responses of inner medullary methylamines and polyols to 5 days of salt loading were investigated. Salt loading increased plasma sodium concentration and induced a saline diuresis that resulted in a significantly lower urine osmolality (Uosmol) in salt-loaded rats (1,246 mosmol) compared with controls (2,147 mosmol). Analysis of inner medullary organic osmolytes using 1H-NMR spectroscopy and biochemical assays indicated no significant change in total methylamines, total polyols, or total osmolytes with salt loading. However, there were marked changes in individual organic osmolytes. Renal inner medullary glycerophosphorylcholine (GPC) was 41% lower in salt-loaded rats, and was the only organic osmolyte that changed in parallel with Uosmol, which was 42% lower in this group. In contrast, glycine betaine (betaine) and sorbitol contents were elevated by 286% and 33%, respectively, with salt loading, and myo-inositol (inositol) was unchanged. These findings indicate selective renal inner medullary osmolyte responses to salt loading with only GPC varying directly with changes in urine osmolality.

Animals↗
PubMed1997

Urea and methylamines have similar effects on aldose reductase activity.

The concentration of urea in renal medullary cells is sufficiently high to inhibit activity of many enzymes, yet the cells survive and function. The generally accepted explanation is the counteracting osmolytes hypothesis, which holds that methylamines, such as glycerophosphorylcholine (GPC) and glycine betaine (betaine), found in the renal medulla stabilize biological macromolecules and oppose the effects of urea. The present study tests this hypothesis by determining the effects of urea and methylamines, singly and in combination, on the activity of aldose reductase, an enzyme that is important in renal medullas for catalyzing production of sorbitol from glucose. In apparent contradiction to the counteracting osmolytes hypothesis, urea (1.0 M) and three different methylamines (trimethylamine N-oxide, betaine, and GPC; 0.5 M) all have similar and partially additive inhibitory effects. They all decrease substantially both the Michaelis constant (K(m)) and the maximum velocity (Vmax). Also a high concentration (0.5 M) of other organic osmolytes that are abundant in the renal medulla, namely inositol, sorbitol, or taurine, has a similar but lesser effect. KCl (0.3 M) causes a small increase in activity. We discuss the significance of these findings with regard to function of aldose reductase in the renal medulla and the counteracting osmolytes hypothesis.

Aldehyde Reductase↗
PubMedDate not supplied

Methylamines and polyols in kidney, urinary bladder, urine, liver, brain, and plasma. An analysis using 1H nuclear magnetic resonance spectroscopy.

Methylamines and polyols are known to behave as organic osmolytes in the adaptation of many cells to hyperosmolar conditions. Using 1H nuclear magnetic resonance spectroscopy to analyze perchloric acid extracts we have examined several tissues in the rat for the presence of these compounds. Methylamines such as glycerophosphorylcholine, choline and betaine were observed in the renal inner medulla, urinary bladder, urine, liver, brain, and plasma. Myoinositol was relatively abundant in the renal inner medulla and brain whereas sorbitol was detected only in the inner medulla. A variety of unidentified compounds was also detected in each tissue. Although these methylamines and polyols are known to respond to osmotic changes in the renal inner medulla, their responses in other tissues remain to be investigated.

Animals↗
PubMed1993

Metabolic formation of dimethylamine and methylamine from basic drugs containing N-methyl group: a newly established chromatographic assay and its application to the determination of deaminase activity.

A new method of assaying deaminase activity was established in which methylamine and/or dimethylamine formed from drugs containing N,N-dimethyl or N-methyl group were derivatized with phenylisothiocyanate to phenylthiourea derivatives. After purification with Sep-PAK C18 cartridge, the derivatives were separated by a reversed phase high-performance liquid chromatography monitored by ultraviolet absorption. The recoveries and determination limits of methylamine and dimethylamine were over 55% and about 0.4 nmol/ml of incubation mixture, respectively. The method was used to measure the deaminase activities of liver microsomes of rats, rabbits and guinea pigs for 11 drugs. Of the compounds tested, diphenhydramine and diltiazem are deaminated with microsomes from all the above animal species; rat and rabbit liver microsomes also well deaminated promethazine. Most other drugs such as chlorpromazine, promazine, imipramine, amitriptyline and tetracaine were found to be poor substrates. In general, dimethylamine but not methylamine was the predominant metabolite formed from drugs containing N,N-dimethylamino group. The results also suggested that the deamination of these compounds takes place mainly via a one step mechanism, thus implying that the sequential reaction consisting of N-demethylation and elimination of ammonia is of minor importance. The relation between in vitro deaminase activity and the extent of the in vivo deamination for drugs is discussed.

Aminohydrolases↗
PubMed2005

Effect of oral creatine supplementation on urinary methylamine, formaldehyde, and formate.

PURPOSE: It has been claimed that oral creatine supplementation might have potential cytotoxic effects on healthy consumers by increasing the production of methylamine and formaldehyde. Despite this allegation, there has been no scientific evidence obtained in humans to sustain or disprove such a detrimental effect of this widely used ergogenic substance. METHODS: Twenty young healthy men ingested 21 g of creatine monohydrate daily for 14 consecutive days. Venous blood samples and 24-h urine were collected before and after the 14th day of supplementation. Creatine and creatinine were analyzed in plasma and urine, and methylamine, formaldehyde, and formate were determined in 24-h urine samples. RESULTS: Oral creatine supplementation increased plasma creatine content 7.2-fold (P < 0.001) and urine output 141-fold (P < 0.001) with no effect on creatinine levels. Twenty-four-hour urine excretion of methylamine and formaldehyde increased, respectively, 9.2-fold (P = 0.001) and 4.5-fold (P = 0.002) after creatine feeding, with no increase in urinary albumin output (9.78 +/- 1.93 mg x 24 h(-1) before, 6.97 +/- 1.15 mg x 24 h(-1) creatine feeding). CONCLUSION: This investigation shows that short-term, high-dose oral creatine supplementation enhances the excretion of potential cytotoxic compounds, but does not have any detrimental effects on kidney permeability. This provides indirect evidence of the absence of microangiopathy in renal glomeruli.

Administration, Oral↗
PubMed2003

14C-methylamine-glutaraldehyde conjugation as an alternative to iodination for protein labeling.

Radiolabeling of native proteins conventionally has required iodination using 125Iodine (125I). Although radioiodination can result in high specific activity, there are several drawbacks in the use of 125I (e.g., radiological hazards and short half-life). 14C-Methylamine-glutaraldehyde conjugation to proteins offers an alternative for radiolabeling of proteins that is safer and longer-lived alpha-2-Macroglobulin was radiolabeled by conjugation to a 14C-methylamine-glutaraldehyde conjugate. Analysis of the labeling procedure was performed using scintillation counting, gel filtration chromatography, and protein assays. The radiolabeled alpha-2-macroglobulin was activated using established protocols and tested for functional integrity using competitive binding assays in the presence of recombinant receptor associated protein, an alternative ligand for the alpha-2-macroglobulin cellular receptor. The function of alpha-2-macroglobulin was unaffected by the labeling procedure. Comparison of 14C-methylamine-labeling and iodination by Scatchard analysis yielded nonlinear plots that suggested the presence of two sets of receptors with different binding affinities but that do not show cooperativity. This technique offers an alternative to radioiodination for the sensitive labeling of proteins.

Binding, Competitive↗
PubMedDate not supplied

[Parthenogenetic development in response to the treatment of mouse oocytes with a weak alkali. Experiments with methylamine].

Ovulated mouse oocytes were incubated in methylamine-containing medium M16 for different periods of time. Methylamine appeared to activate oocytes, and most of them developed by haploid parthenogenesis. Methylamine action depended on its concentration and time of incubation. The data obtained suggest that the increase of intracellular pH unblocks meiosis and activates mammalian oocytes [correction of cocytes].

Animals↗
PubMed1988

Effects of organic solvents, methylamines, and urea on the affinity for Pi of the Ca2+-ATPase of sarcoplasmic reticulum.

The Ca2+-ATPase of sarcoplasmic reticulum can be phosphorylated by Pi, forming an acylphosphate residue at the catalytic site of the enzyme. In a previous report (de Meis, L., Alves, E., and Martins, O.B. (1980) Biochemistry 19, 4252-4261), it was shown that organic solvent such as dimethyl sulfoxide and glycerol cause a decrease in the apparent Km for Pi. In this report it is shown that a similar effect is obtained with the methylamines glycine betaine and trimethylamine N-oxide. The apparent Km value for Pi in totally aqueous medium and in the presence of either 6.4 M glycerol, 1.4 M dimethyl sulfoxide, 0.4 M trimethylamine N-oxide, or 1 M glycine betaine were found to be respectively 2.85, 0.52, 0.52, 0.81, and 0.93 mM at pH 6.2 and greater than 10.0, 1.08, 2.53, 3.05, and 2.05 mM at pH 7.5. In contrast to the effect of methylamines, urea caused an increase in the apparent Km for Pi. When mixed in the appropriate concentration ratio, the effect of either organic solvent or methylamines is cancelled by urea.

Animals↗
PubMed1982

Urea and methylamine effects on rabbit muscle phosphofructokinase. Catalytic stability and aggregation state as a function of pH and temperature.

The effects of urea and several methylamine solutes on the catalytic stability and aggregation properties of rabbit muscle phosphofructokinase were assessed at physiologically realistic concentrations of the solutes under several pH and temperature regimes. The loss of catalytic activity observed under conditions of pH-induced cold lability was significantly reduced in the presence of trimethylamine-N-oxide, N-trimethylglycine and N-methylglycine (order of decreasing effectiveness). The concentration-dependent methylamine stabilization of the enzyme, seen with as little as 50 mM trimethylamine-N-oxide, was accompanied by increased aggregation of the enzyme to molecular weights greater than the tetramer (polytetramer) as solute concentration was raised to 400 mM. At pH 6.5-6.7 and 25 degrees C, concentrations of urea greater than 25 mM promoted a time-dependent inactivation of the enzyme which was enhanced at lower temperatures. The urea sensitivity of the enzyme exhibited with 0.8 M urea for 1 h at pH 8.0 did not result in measurable inactivation. The fluorescence emission wavelength maximum of the enzyme was shifted to longer wavelengths and the fluorescence intensity was increased as pH was lowered to 7.0, suggesting the occurrence of a protein conformation change as specific amino acid residues of the tetramer became protonated. Measurements of enzyme light scattering indicated that perturbation by urea was correlated with tetramer dissociation, which was irreversible by dialysis at 25 degrees C. The urea and methylamine influences on phosphofructokinase activity and structure were not counteracting. The synergistic interactions among pH, temperature, and solutes observed with phosphofructokinase are compared to effects on other associating-dissociating protein systems in order to evaluate possible mechanisms of action of these low molecular weight solutes.

Animals↗
PubMed1983

Ammonium chloride and methylamine hydrochloride antagonize clostridial neurotoxins.

Ammonium chloride (1-8 mM) and methylamine hydrochloride (1-16 mM) produce concentration-dependent antagonism of the onset of neuromuscular blockade caused by botulinum toxin types A, B and C (all at 1 X 10(-11) M) and by tetanus toxin (3 X 10(-10) M). Neither drug antagonizes the onset of paralysis caused by beta-bungarotoxin (1 X 10(-7) M) or by taipoxin (1 X 10(-8) M). At concentrations that produce antagonism of clostridial neurotoxins, ammonium chloride and methylamine hydrochloride (8-10 mM) do not inactivate toxin molecules, nor do they produce irreversible changes in tissue function. When studied under conditions that impose partial synchrony on the mechanism of clostridial neurotoxin action, ammonium chloride and methylamine hydrochloride do not inhibit ligand binding and do not reverse neuromuscular blockade. The drugs act solely to antagonize internalization of toxins by cholinergic nerve endings. As a result of inhibiting the process of internalization, the drugs trap the toxins at an antitoxin sensitive site.

Ammonium Chloride↗
PubMed1992

Cofactor-directed inactivation by nucleophilic amines of the quinoprotein methylamine dehydrogenase from Paracoccus denitrificans.

Phenylhydrazine, semicarbazide, aminoguanidine, hydrazine, and hydroxylamine each irreversibly inactivated methylamine dehydrogenase from Paracoccus denitrificans and caused changes in the absorbance spectrum of the protein-bound tryptophan tryptophylquinone [TTQ] prosthetic group. Different spectral perturbations were observed on reaction with each of these inactivators. In each case a stoichiometry of 2 mol per mol of enzyme (1:1 per cofactor) was required to observe complete modification of the absorbance spectrum. Identical changes were observed in the presence and absence of oxygen. The reactions of hydrazine and hydroxylamine were very rapid, with stoichiometric inactivation occurring in less than 30 s. Inactivation by phenylhydrazine and semicarbazide exhibited apparent bimolecular kinetics and second order rate constants for inactivation, respectively, of 25 min-1 mM-1 and 39 min-1 mM-1. In contrast, inactivation by aminoguanidine exhibited saturation behavior and kinetic parameters of KI = 2.5 mM and kinact = 0.5 min-1 were obtained. Ammonium salts did not inactivate the enzyme, but were reversible competitive inhibitors with respect to methylamine. A Ki of 20 mM was obtained for ammonium chloride. A mechanism for the reactions of these compounds with the TTQ cofactor of methylamine dehydrogenase is proposed, and the relationship of these data to the mechanisms of interaction of these compounds with o-quinones and other quinoproteins which possess TTQ and other quinone cofactors is discussed.

Amines↗
PubMed1995

Reaction mechanism for the inactivation of the quinoprotein methylamine dehydrogenase by phenylhydrazine.

Phenylhydrazine has previously been shown to be an irreversible inactivator of the tryptophan tryptophylquinone (TTQ) enzyme methylamine dehydrogenase [Davidson, V.L. and Jones, L.H. (1992) Biochim. Biophys. Acta 1121, 104-110]. Structure-reactivity correlations have been performed to elucidate the mechanism by which this inactivation occurs. The reactions of a series of p-substituted phenylhydrazines with methylamine dehydrogenase were examined. Correlation with electronic substituent effects was observed. A Hammett plot of the second order inactivation rate constants versus sigma p exhibited a positive slope. Plots of these rate constants against substituent constants which reflected either resonance or field/inductive parameters for each p-substituent indicated that the rate was primarily influenced by resonance electronic effects. A Brønsted plot of the inactivation rate constant against pKa of each substituted phenylhydrazine yielded a beta-value (slope) of 0.7. Based upon these results, a reaction mechanism is proposed for the inactivation of methylamine dehydrogenase by phenylhydrazines, and a structure is proposed for the putative transition state for the rate-limiting step in the overall processes of binding and adduct formation by phenylhydrazine. The relevance of these results to the process of imine formation between substrate amines and TTQ during the normal catalytic process is also discussed.

Indolequinones↗
PubMed2003

Catching catalysis in the act: using single crystal kinetics to trap methylamine dehydrogenase reaction intermediates.

Methylamine dehydrogenase (MADH) is produced by a range of gram-negative methylotrophic and autotrophic bacteria, and allows the organisms to utilise methylamine as the sole source of carbon. The enzyme catalyses the oxidation of methylamine to formaldehyde and ammonia, leaving it in a two-electron reduced state. To complete the catalytic cycle, MADH is reoxidised via an electron transfer (ET) chain. The redox center in the enzyme is the organic cofactor tryptophan tryptophylquinone (TTQ) derived from the posttranslational modification of two Trp residues in the protein. This cofactor has spectral features in the visible region, which change during catalytic turnover, defining spectrally distinct reaction intermediates that reflect the electronic state of the TTQ. In the case of the Paracoccus denitrificans enzyme the physiologic ET chain involves the protein redox partner amicyanin (a blue copper protein). A stable binary (MADH/amicyanin) complex can be formed, and its crystal structure has been solved to 2.5 A resolution by Chen et al. [Biochemistry 21 (1992) 4959]. These crystals were shown to be competent for catalysis and ET by Merli et al. [J. Biol. Chem. 271 (1996) 9177] using single crystal polarised absorption spectroscopy. Through a novel combination of single crystal visible microspectrophotometry, X-ray crystallography and freeze-trapping, we have trapped reaction intermediates of the enzyme in complex with its physiological redox partner amicyanin in the crystalline state. We will present data confirming that catalysis and ET in the binary complex crystals can be tracked by single crystal visible microspectrophotometry. We will also show that the reaction pathway is unperturbed by the presence of cryoprotectant solution, enabling direct freeze-trapping of reaction intermediates within the crystal. We will present new data demonstrating that the binary complex crystals are also capable of exhibiting UV light-dependent oxidase activity, as observed in solution [Biochim. Biophys. Acta 1364 (1998) 297].

Bacterial Proteins↗
PubMed1995

Intermolecular electron transfer from substrate-reduced methylamine dehydrogenase to amicyanin is linked to proton transfer.

Within the methylamine dehydrogenase-amicyanin complex, intermolecular electron transfer (ET) occurs between tryptophan tryptophylquinone (TTQ) and copper. The ET reactions from two chemically distinct reduced forms of TTQ were studied. The quinol form of TTQ was generated by reduction by dithionite. An aminoquinol form of TTQ, in which an amino group displaces the carbonyl oxygen, was generated by reduction by the substrate methylamine. Thermodynamic analysis of the ET reactions suggested that the ET event was rate-limiting for the redox reaction between quinol TTQ and copper, but not for the ET reaction from aminoquinol TTQ to copper. Solvent kinetic isotope effect studies indicated that proton transfer was involved in the rate-limiting reaction step for the ET from the substrate-reduced enzyme, but not the dithionite-reduced enzyme. Solvent deuterium kinetic isotope effects of 1.5 and 12.2 were obtained, respectively, for the ET reactions from dithionite-reduced and substrate-reduced methylamine dehydrogenase. These results demonstrate that application of ET theory to the analysis of thermodynamic data for the intermolecular protein ET reactions can potentially be used to distinguish between true ET reactions and those which are gated or attenuated by adiabatic events. Kinetic models are presented to explain how the incorporation of the substrate-derived amino group into TTQ may alter the rate-limiting step for ET.

Bacterial Proteins↗
PubMed1991

Resonance Raman spectroscopy of methylamine dehydrogenase from bacterium W3A1.

Resonance Raman spectroscopy has been used to probe the structure of the covalently bound quinone cofactor in methylamine dehydrogenase from the bacterium W3A1. Spectra were obtained on the phenylhydrazine and 2-pyridylhydrazine derivatives of the native enzyme, on the quinone-containing subunit labeled with phenylhydrazine, and on an active-site peptide also labeled with phenylhydrazine. Comparisons of these spectra to the corresponding spectra of copper-containing amine oxidase derivatives indicate that the quinones in these two classes of quinoproteins are not identical. The resonance Raman spectra of the native enzyme and small subunit have also been measured. 16O/18O exchange permitted the carbonyl modes of the quinone to be identified in the resonance Raman spectrum of oxidized methylamine dehydrogenase: a band at 1614 cm-1, together with a shoulder at 1630 cm-1, are assigned as modes containing substantial C = O stretching character. D2O/H2O exchange has pronounced effects on the resonance Raman spectrum of the oxidized enzyme, suggesting that the quinone may have numerous hydrogen bonds to the protein or that it is unusually sensitive to the local environment. Resonance Raman spectra of the isolated small subunit, and its phenylhydrazine derivative, are considerably different from the corresponding spectra of the intact protein. An attractive explanation for these observations is that the quinone cofactor in methylamine dehydrogenase from W3A1 is located at the interface between the large and small subunits, as found for the enzyme from Thiobacillus versutus [Vellieux, F. M. D., Huitema, F., Groendijk, H., Kalk, K. H., Frank, J. Jzn., Jongejan, J. A., & Duine, J. A. (1989) EMBO J. 8, 2171-2178].(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1996

Electrostatic environment of the tryptophylquinone cofactor in methylamine dehydrogenase: evidence from resonance Raman spectroscopy of model compounds.

Methylamine dehydrogenase (MADH) utilizes its endogenous tryptophan tryptophylquinone (TTQ) as a cofactor in enzymatic catalysis, with the C6 carbonyl of the quinone implicated as the site of attack by substrates and other nucleophiles. Resonance Raman (RR) spectroscopy provides an ideal method for investigating the state of this carbonyl group whose C==O stretch is distinct from other vibrational modes of the cofactor and is readily identified by its shift to lower energy in H218O. In a series of indole 6,7-quinone models for TTQ, the in-phase stretching vibration of the two C==O groups occurs at 1650 cm-1 in nonpolar solvents and shifts to 1638 cm-1 in H2O. The absorption maximum undergoes an analogous shift from 400 to 425 mm. The spectral properties of the indole quinones in H2O approach the corresponding values in Thiobacillus versutus MADH (C==O stretch at 1612 cm-1, lamdamax at 440mm) and are indicative of strongly hydrogen bonding of the C==O and NH groups of the cofactor in the native enzyme. Addition of monovalent cations [NH4+,Cs+, and (CH3)3NH+] to MADH causes further increases in the lamdamax and decreases in the frequency of the C==O stretch[1590 cm-1 with (CH3)3NH+]. This implies a strong electrostatic interaction between monovalent cations and a carbonyl oxygen (most likely at C6) in TTQ. The fact that these cations behave as competitive inhibitors of the methylamine substrate suggests that methylamine binds to the same location in the enzyme prior to its covalent reaction with the cofactor. Addition of monovalent cations to the one-electron-reduced semiquinone form MADH results in RR spectral shifts for a number of vibrational modes of the cofactor. Thus, the ability of monovalent cations to promote and stabilize the formation of the semiquinone intermediate is also due to their direct electrostatic interaction with the TTQ cofactor.

Catalysis↗
PubMed1996

Evidence for a tryptophan tryptophylquinone aminosemiquinone intermediate in the physiologic reaction between methylamine dehydrogenase and amicyanin.

The tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase (MADH) is covalently modified by nitrogen during its two-electron reduction by methylamine to form an aminoquinol (N-quinol). It is possible, in vitro, to generate unmodified O-quinol and O-semiquinone forms of MADH with dithionite, as well as an N-semiquinone form which contains a substrate-derived nitrogen. Rapid-scanning stopped-flow spectroscopy and global kinetic analysis are used to demonstrate that N-semiquinone is a true physiologic reaction intermediate which accumulates during the two sequential one-electron oxidations of N-quinol MADH by amicyanin. In contrast, no detectable O-semiquinone accumulates during the two sequential one-electron oxidations of the O-quinol form of MADH by amicyanin. This is because the reaction of N-semiquinone with amicyanin is much slower (70 s-1 at 25 degrees C) than the reaction of O-semiquinone ( > 1000 s-1). These rate constants obtained from global analysis of the overall reaction are the same as those obtained when each semiquinone form was made in vitro and then mixed with oxidized amicyanin. The presence of 200 mM NH4Cl during the reaction of O-quinol MADH with amicyanin does not cause any detectable accumulation of a semiquinone species. Thus, the accumulation of the intermediate in the reactions of the N-quinol is not due to the influence of noncovalently bound ammonia at the active site of the O-semiquinone. These data indicate that the intermediate which accumulates during the complete oxidation of substrate-reduced N-quinol MADH is not the O-semiquinone, but the more slowly reacting N-semiquinone, and that the N-semiquinone is a physiologically relevant reaction intermediate. These results also provide good evidence in favor of an aminotransferase mechanism, as opposed to an imine elimination mechanism, for the reaction of MADH with substrate methylamine.

Ammonium Chloride↗