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B Mondovi

Publications and source records attributed to B Mondovi.

At least 19 recordsLinked to original sources
PubMed2003

Is the catalytic mechanism of bacteria, plant, and mammal copper-TPQ amine oxidases identical?

This short review is mostly concerned with the work carried out in Rome on the copper amine oxidase from bovine serum (BSAO). The first target was the copper oxidation state and its relationship with the organic cofactor. It was found that copper is not reduced on reaction with amines under anaerobic conditions or along the catalytic cycle and that it is not within bonding distance of the quinone cofactor. The copper stability in the oxidised state was supported by BSAO ability to oxidise benzylhydrazine, a slow substrate, in the presence of N,N-diethyldithiocarbamate (DDC) and by the substantial catalytic activity of Co(2+)-substituted BSAO. Parallel work established that only one subunit of the dimeric enzyme readily binds reagents of the carbonyl group. Flexible hydrazides with a long aromatic tail were found to be highly specific inhibitors, suggesting the presence of an extended hydrophobic region at the catalytic site. A study by stopped-flow transient spectroscopy and steady state kinetics led to the formulation of a simplified, yet complete and consistent, catalytic mechanism for BSAO that was compared with that available for lentil seedling amine oxidase (LSAO). As in other copper amine oxidases, BSAO is inactivated by H(2)O(2) produced in the catalytic reaction, while the cofactor is stabilised in its reduced state. A conserved tyrosine hydrogen-bonded to the cofactor might be oxidised.

Amine Oxidase (Copper-Containing)↗
PubMed2002

Tyramine and monoamine oxidase inhibitors as modulators of the mitochondrial membrane permeability transition.

Incubation of rat liver mitochondria with 100-500 mM tyramine, a substrate for monoamine oxidases A and B (MAOs), in the presence of 30 mM Ca2+ induces matrix swelling, accompanied by collapse of membrane potential, efflux of endogenous Mg2+ and accumulated Ca2+ and oxidation of endogenous pyridine nucleotides. These effects are completely abolished in the presence of cyclosporin A, ADP, dithioerythritol and N-ethylmaleimide, thus confirming the induction of the mitochondrial membrane permeability transition (MPT). The observed partial protective effect exerted by catalase indicates the involvement of both MAO-derived hydrogen peroxide and aldehyde. Higher concentrations of tyramine (1-2 mM) are less effective or even completely ineffective. At these high concentrations tyramine has an inhibitory effect when the MPT is induced by 100 mM Ca2+. The MAO inhibitors clorgyline (50 mM) and pargyline (500 mM) completely protect against MPT induction by 100 mM tyramine but also inhibit the phenomenon, although with different efficacy, when it is induced by 100 mM Ca2+ in the absence of tyramine. Taken together, our data suggest that tyramine, clorgyline and pargyline act as modulators of the MPT either through a direct inducing/protective effect or by controlling hydrogen peroxide and aldehyde generation.

Animals↗
PubMed2001

Redox properties and acid-base equilibria of zucchini mavicyanin.

The reduction potential of mavicyanin isolated from zucchini peelings, which is a blue copper protein belonging to the subclass of the phytocyanins, has been determined through direct electrochemistry as a function of temperature and pH. The enthalpy and entropy changes accompanying protein reduction were found to be very similar with those determined previously for other phytocyanins and to differ remarkably from those of azurins and plastocyanins. This finding contributes to further characterize phytocyanins as a distinct cupredoxins family also on thermodynamic grounds and improves our understanding of how the reduction potential of these metal centers in proteins is modulated by coordinative and solvation properties. The E degrees' of mavicyanin is found to be sensitive to two acid-base equilibria at the extremes of pH. One occurs below pH 4, and is related to the protonation and detachment from the Cu(I) center of a histidine ligand. The other, observed above pH 8, causes a remarkable change in the electrostatic potential and/or the field strength around the copper.

Journal Article↗
PubMed1998

Protection against apoptosis by monoamine oxidase A inhibitors.

Several lines of evidence have been accumulating indicating that an important role may be played by mitochondrial homeostasis in the initiation phase, the first stage of apoptosis. This work describes the results obtained by using different inhibitors of monoamine oxidases (MAO), i.e. pargyline, clorgyline and deprenyl, on mitochondrial integrity and apoptosis. Both pargyline and clorgyline are capable of protecting cells from apoptosis induced by serum starvation while deprenyl is ineffective. These data represent the first demonstration that MAO-A inhibitors may protect cells from apoptosis through a mechanism involving the maintenance of mitochondrial homeostasis.

Apoptosis↗
PubMed1998

Inhibitory effect of 1,3,5-triphenyl-4,5-dihydro-(1H)-pyrazole derivatives on activity of amine oxidases.

A new series of 1,3,5-triphenyl-4,5-dihydro-(1H)-pyrazole derivatives was synthesized to ascertain the contribution of substituted phenyl rings present on the 4,5-dihydro-(1H)-pyrazole nucleus to the monoamine oxidases inhibition and bovine serum amine oxidase inhibition. All compounds were tested on bovine brain mitochondria preparation containing flavin-monoamine oxidases and on purified bovine serum amine oxidases, taken as a model of trihydroxyphenylalanine quinone-copper-containing amine oxidases. The 1,3,5-triphenyl-4,5-dihydro-(1H)-pyrazole derivatives showed a good inhibitory activity and belonged to the third generation of monoamine oxidase inhibitors and bovine serum amine oxidase inhibitors which have the advantage of acting through a reversible mode. Furthermore, their activity showed a good degree of selectivity towards the bovine serum amine oxidase inhibition dependent on the substituents present on the phenyl ring at position 5 of the 4,5-dihydro-(1H)-pyrazole.

Animals↗
PubMed1998

Characterization of the haemoglobin-mediated inhibition of the enzymatic activity of bovine serum amine oxidase.

Haemoglobin has been previously identified as responsible for the decreased enzymatic activity of copper bovine serum amine oxidase (BSAO) in suspensions of human or bovine hemolyzed erythrocytes [Marcocci, L., Pietrangeli, P., Befani, O., Mavelli, I., & Mondovi', B. (1991b) Life Chem. Report, 9, 171-177]. This is confirmed by present results on bovine methaemoglobin. Bovine globin and horse skeletal muscle mioglobin showed a similar inhibiting ability, but neither bovine serum albumin nor cytochrome c inhibited BSAO activity under the same experimental conditions. The inhibitory effect of bovine haemoglobin was dependent on pH only at high buffer ionic strength. It was highest in physiological conditions (PBS) where haemoglobin acted as a reversible non competitive inhibitor of BSAO activity, with apparent Ki of 0.5 mM at 37 degrees C. The inhibition was unaffected by partial BSAO deglycosylation (40% of glucidic residues removed) but decreased when haemoglobin lysine groups were derivatised using citraconic anhydride. A possible molecular mechanism underlying the inhibitory effect is discussed.

Amine Oxidase (Copper-Containing)↗
PubMed1996

Extended substrate specificity of serum amine oxidase: possible involvement in protein posttranslational modification.

The capacity of bovine serum amineoxidase (SAO) to oxidize free amino groups of nonconventional substrates, such as polylysine (up to 50 kDa) and some proteins as lysozyme and ribonuclease A, is described. The oxidation was quantified from the amount of H2O2 and NH3 enzymatically produced by SAO. Kinetic analysis indicated a stereospecific preference for L-configuration. Maximal oxidation rate was obtained with poly-L-lysine (9.6 kDa). After 10 h of incubation at 37 degrees C, the poly-L-lysine was partially oxidized generating 1.5 moles of H2O2 by one mole of polylysine. Denatured SAO presented very low oxidation rates with the mentioned substrates.

Amine Oxidase (Copper-Containing)↗
PubMed1996

Modulation of K+ channel currents by serum amineoxidase in neurons.

The influence of bovine serum amineoxidase (SAO), a circulating copper-enzyme, on neuronal K+ channels is described. Bovine SAO enhanced K+ channel currents in N1E-115 neuroblastoma cells in a time-dependent manner. Unlike ceruloplasmin (another copper-protein, shown as depolarizing factor in neurons), SAO had no effect on resting potential of neurons. However, pretreatment of cells with SAO inhibited ceruloplasmin-induced membrane depolarization. Although ceruloplasmin alone inhibited K+ channel currents, it further enhanced K+ channel currents in the presence of SAO. Therefore, SAO may be another endogenous modulator of neuronal K+ channels with effect and mechanisms different from those of ceruloplasmin.

Amine Oxidase (Copper-Containing)↗
PubMed1995

Inhibition of diamine oxidase activity by metronidazole.

Metronidazole was found to be a non-competitive inhibitor of man, rabbit and rat intestinal diamine oxidases with an inhibition constant value of approximately 10(-4) M. The purified bovine serum amine oxidase was not inhibited, whereas the purified swine kidney enzyme gave similar results. These findings suggest that metronidazole and similar compounds, used as antibacterial and antiprotozoal drugs, should be given under careful control, especially when administered for long times, because a decrease of intestinal diamine oxidase activity was proven to be a risk factor for several pathologies of this organ.

Amine Oxidase (Copper-Containing)↗
PubMed1994

Heat enhancement of cytotoxicity induced by oxidation products of spermine in Chinese hamster ovary cells.

This study investigates the potential of using polyamines as thermosensitizers, in the presence of bovine serum amine oxidase (BSAO), as a new anticancer strategy. The effect of hyperthermia on cytotoxicity of spermine oxidized by purified bovine serum amine oxidase was investigated in Chinese hamster ovary cells. Several different spermine concentrations were employed in the presence of BSAO at 37 degrees and 42 degrees. Cytotoxicity was considerably enhanced at 42 degrees. Heat also increased the individual cytotoxicity of both exogenous H2O2 and the exogenous aldehyde acrolein. Thus, both of these species could contribute to the thermal enhancement of cytotoxicity caused by BSAO and spermine. The effect of temperature was especially marked in the presence of exogenous catalase. This cytotoxicity cannot be accounted for by H2O2 and was attributed to aldehyde(s). The involvement of aldehyde(s) in cytotoxicity at 42 degrees was also confirmed by the complete inhibition of cytotoxicity with both exogenous aldehyde dehydrogenase and exogenous catalase. A particularly interesting finding, in the presence of exogenous catalase, was that conditions of BSAO and spermine (< or = 50 microM) which were non-toxic at 37 degrees became cytotoxic at 42 degrees. This suggests that spermine-derived aldehyde(s), that were non-toxic at 37 degrees, contributed to cytotoxicity at 42 degrees and resemble thermosensitizers. The thermosensitizing activity of aldehyde(s) produced in the BSAO-catalysed oxidation of spermine has potential value for improving the therapeutic effects of hyperthermia and could be considered for future application in cancer therapy. Polyamines are present at elevated levels in tumour cells and have been considered as heat sensitizers. By delivering BSAO into tumour cells, toxic oxidation products of polyamines could be produced in situ for selective killing of tumour cells.

Aldehyde Dehydrogenase↗
PubMed1994

Electrostatic control of oxidative deamination catalysed by bovine serum amine oxidase.

The ionic-strength-dependence of steady-state kinetic parameters (kc and Km') for non-biogenic (benzylamine, butylamine) and biogenic (spermine, spermidine) amines has been measured in the bovine serum amine oxidase reaction. The catalytic rate constant (kc) values are similar (0.9-2.5 s-1) for all the substrates studied and are almost constant over the experimental ionic strength range (24-155 mM). In contrast, Km' values are in the range 6-2300 microM and undergo a 4-12-fold increase with increasing ionic strength, parallelled by a decrease in catalytic efficiency. From an analysis of the kc and Km' values and their dependence on ionic strength, we conclude that more than one negative site is involved in the binding of these amines and that the relative dielectric constant of the binding site is lower than that of aqueous solutions.

Amine Oxidase (Copper-Containing)↗
PubMed1994

Joint chromatographic purification of bovine serum ceruloplasmin and amineoxidase.

A purification procedure leading to a joint separation of two serum copper-enzymes: ceruloplasmin (EC 1.16.3.1) and amineoxidase (EC 1.4.3.6), is described. Both enzymes are obtained in electrophoretically homogeneous form and their specific activities are higher than those obtained by previously described purification techniques. Two common steps: precipitation of bovine plasma proteins with ammonium sulphate (at 35% and 55% saturation) followed by column chromatography on AE-Agarose (obtained by treatment of agarose beads with 1-chloro-2-ethylamine), lead to an electrophoretically homogeneous ceruloplasmin. At the same time, the ceruloplasmin-free protein preparation eluted in a first peak, following further Q-Sepharose and Con A-Sepharose chromatography, leads to purified bovine serum amine oxidase (BSAO) with an improved yield. The emphasis was given to a mutual improving effect as a consequence of the integration of the two enzymes purification procedures.

Amine Oxidase (Copper-Containing)↗
PubMed1993

Cytotoxicity and kinetic analysis of purified bovine serum amine oxidase in the presence of spermine in Chinese hamster ovary cells.

Bovine serum amine oxidase (BSAO, EC 1.4.3.6) catalyzes the oxidative deamination of polyamines giving rise to the corresponding aldehydes, ammonia and hydrogen peroxide (H2O2). This study demonstrates that amine oxidase (BSAO) purified from bovine serum and exogenous spermine caused cytotoxicity in Chinese hamster ovary (CHO) cells. Cytotoxicity occurred when cells were exposed to BSAO (0.0164-16.4 micrograms/ml) in the presence of spermine (1.9-340 microM). BSAO and spermine alone were not toxic at these concentrations. Cytotoxicity was dependent on the concentration of spermine and on the incubation time, and was also accelerated at 42 degrees C relative to 37 degrees C. Kinetic analysis of the enzymatic reaction, as a function of spermine concentration, showed Michaelis-Menten saturation kinetics. The apparent Vmax increased from 19.1 +/- 0.4 microM min-1 at 37 degrees C to 23.0 +/- 0.3 microM min-1 at 42 degrees C. The apparent Km decreased from 25.5 +/- 2.6 microM at 37 degrees C to 17.7 +/- 1.3 microM at 42 degrees C. Catalase inhibited cytotoxicity, suggesting that H2O2 was partially responsible for cytotoxicity. This work shows that the oxidation products of polyamines, rather than the polyamines themselves, are responsible for cytotoxicity in mammalian cells. The significance of this study is that amine oxidases could have therapeutic potential in cancer treatment regimens and a beneficial effect is likely when the enzyme is used together with clinical hyperthermia.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Bovine serum amine oxidase: half-site reactivity with phenylhydrazine, semicarbazide, and aromatic hydrazides.

Aromatic hydrazides of the general formula NH2NHCO(CH2)nC6H4R were covalently bound by bovine serum amine oxidase (BSAO), giving rise to optical and CD absorptions at 350-400 nm. Benzohydrazides (n = 0) reacted slowly, in the ratio of one per dimeric protein molecule, like semicarbazide. Phenylacetohydrazides (n = 1) and phenylpropionic hydrazides (n = 2) reacted instead in the ratio of two per dimer, one molecule at a much faster rate than the other. The fast reaction correlated with the loss of enzymatic activity. The contribution to the optical absorbance of either molecule was identical, but only the first one produced a CD band, the wavelength and sign of which were determined by the number n of methylene groups in the hydrazide. In n = 1 and n = 2 compounds, the reaction was faster as the R substituent became more hydrophobic (triazolyl less than imidazolyl less than phenyl), suggesting a specific interaction with the protein matrix. Phenylhydrazine was found to react with the native enzyme in the ratio of only one per protein dimer. However, one phenylhydrazine was also slowly bound by most 1:1 enzyme-hydrazide adducts, with the formation of ternary derivatives. Phenylhydrazine formed the usual intense band at 447 nm with n = 1 and n = 2 hydrazide-BSAO adducts and a weaker, blue-shifted band with the adducts of semicarbazide and of some n = 0 hydrazides. In both cases, the hydrazide absorption band was unaffected. Competition was observed with other benzohydrazides and with the second molecule of n = 1 compounds. A half-site mechanism appears to be operative, the second site being always less reactive than the first. Reactivity and adduct conformation were also affected by N,N-diethyldithiocarbamate, a powerful enzyme inhibitor that binds copper.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Specific temperature dependence of diamine oxidase activity and its thermal stability in the presence of polyvinylalcohol.

An inflexion point on the dependence of the swine kidney diamine oxidase activity upon the temperature was found at 40-43 degrees C, suggesting a conformational transition. The activation energies with putrescine as substrate calculated from the Arrhenius plots were 38.23 kcal/mol for the temperature interval 25-40 degrees C and only 15.14 kcal/mol for the range 45-60 degrees C. These values suggest two different conformations, one corresponding to the interval below 40 degrees C and another one between 43-60 degrees C, with an intermediate transitory form corresponding to the inflexion point at 40-43 degrees C. For various temperature decades within 10-60 degrees C, peculiar Q10 values in the range 1.37-3.00 (differing from the usual value Q10 = 2), were obtained. The non-strictly Arrhenius curves, the activation energies and the inflexion point were quite similar with and without 0.05% polyvinylalcohol. This particular temperature effect found for swine kidney diamine oxidase is similar to the one reported for bovine serum amine oxidase. An increased enzyme thermal stability was obtained in the presence of high molecular weight polyvinylalcohol.

Amine Oxidase (Copper-Containing)↗
PubMed1991

Status of the cofactor identity in copper oxidative enzymes.

Much conflicting data have appeared in the literature regarding the nature of the active site structures responsible for catalysis in three classes of copper enzymes: the copper amine oxidases, dopamine beta-monooxygenase and galactose oxidase. Although pyrroloquinoline quinone has been proposed to be the active site cofactor in each instance, new findings indicate this is not the case. Instead, recently available data indicate a spectrum of strategies for substrate activation, which range from direct metal catalysis (dopamine beta-monooxygenase) to the involvement of protein-derived radicals (galactose oxidase) and protein-derived quinones (copper amine oxidases).

Amine Oxidase (Copper-Containing)↗