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Furin belongs to serine intracellular Ca2+-dependent endopeptidases of the subtilisin family, also known as proprotein convertase (PC). Human furin is synthesized as zymogen with a molecular weight of 104 kDà, which is then activated by autocatalytic in two stages. This process can occur when zymogen migrates from the endoplasmic reticulum to the Golgi apparatus, where a large part of furin is accumulated. The molecular weigh t of the active furin is 98 kDà. Furin relates to enzymes with a narrow substrate specificity: it hydrolyzes peptide bonds at the site of paired basic amino acids and furin activity exhibits in a wide pH range 5-8. Its main biological function is activation of the functionally important protein precursors. It is accompanied by the launch of a cascade of reactions, which lead to appearance of biologically active molecules involved in realization of specific biological functions both in normal and in some patologicheskih processes. Furin substrates are biologically important proteins such as enzymes, hormones, growth factors and differentiation, receptors, adhesion proteins, proteins of blood plasma. Furin plays an important role in the development of processes such as proliferation, invasion, cell migration, survival, maintenance of homeostasis, embryogenesis, as well as the development of a number of pathologies, including cardiovascular, oncologic and neurodegenerative diseases. Furin and furin-like proprotein convertases participate as key factors in the realization of the regulatory functions of proteolytic enzymes, the value of which is currently being evaluated as most important in comparison with the degradative function of proteases.

The paper describes the physiological effects of various biogenic amines, their occurrence in the body, and degradation. It outlines the present views of diversity of flavin adenine dinucleotide-dependent and semicarbazide-sensitive amine oxidases. Methods for preparation of various tissue extracts and spectrophotometric and radiation techniques for determination of the activity of these enzymes, by using various substrates, are described.

An aim of the paper was to study some biochemical parameters of drug-naïve patients with the first episode of schizophrenia. Activities of platelet monoaminooxidase (MAO) and semicarbazide, a sensitive blood serum aminooxidase (BSA), levels of middle-sized molecules (MSM) and malonic dialdehyde (MDA), parameters of functional state of serum albumin were assessed in 16 patients. Severity of symptoms in patients with the first episode of schizophrenia was assessed as moderate (PANSS scores 73.1+/-12.5) before the treatment. The increase of MAO by 107%, reduction of BSA by 29% and increase of MSM level by 140% was found in patients compared to controls (p<0.01). The study of other biochemical (MDA level) and biophysical (effective albumin concentration) parameters did not yield unequivocal results. It has been suggested that MAO and BSA are integral components of pathogenetic mechanisms in patients with the first episode of schizophrenia.

Seasonal variations of recovery of liver monoamine oxidase activity were studied in different subcellular fractions after administration of a large dose of pargyline in vivo. It was shown that the recovery of cytosolic MAO differs greatly from the membrane bound forms in the rate of reconstitution of its activity upon irreversible inhibition in vivo. Alcoholization leads to a decrease of the rate of recovery of only the membrane-bound but not a cytosolic MAO B forms in rat liver.

The study experimentally assessed the approach proposed by the authors to lower alcohol motivation, which involves enhancement of a specific immunity at the stage of alcoholization when acetaldehydemodified ethanol exchange enzymes [alcohol dehydrogenase (ADH)] and acetaldehyde dehydrogenase may be expected to occur. Omega-3 polyunsaturated fatty acid (PUFA) drugs enhance the formation of autoantibodies to modified ADH and decrease the activity of ADH in the stomach and liver. At the same time, PUFA drugs can, under certain conditions, produce an anti-alcoholic activity and a positive effect on the psychoemotional status of animals after the ethanol deprivation period.

Experimental results have demonstrated a significant decrease in the level of alcohol consumption by albino rats immunized with heterologous horse alcohol dehydrogenase. The role of ADH epitopes 9-14, 93-115, and 265-276 in this phenomenon was examined, and it was established that the latter sequence (265-276) plays the biggest role. The inhibition of ADH activity in the adrenals of immunized rats was much higher compared to the liver. We propose a hypothesis that the effect of alcohol dehydrogenase on alcohol consumption is connected with its role in catecholamine metabolism.

The sensitivity of mitochondrial and cytosolic monoamine oxidase (MAO) activities to inhibition by specific irreversible inhibitors was investigated. There were no significant differences in the sensitivity of MAO A and MAO B activities of these fractions to selective inhibitors. However, in vivo administration of pargyline caused a much more potent inhibition of cytosolic MAO than the mitochondrial enzymes. This suggests that cytosolic MAO activity does not represent an artifact (e.g. a product of proteolytic degradation) appearing after tissue homogenisation. The higher sensitivity of cytosolic MAO to inhibitors also points to different routes for pargyline to inhibit MAO in these subcellular fractions.

The range of the biochemical reactions which can be catalyzed by ADH I and ADH IV is extremely wide. The most characterized functions of these enzymes are protection against excess endogenous acetaldehyde, products of lipid peroxidation, exogenous alcohols and some xenobiotics. It was found also that ADH I and ADH IV are important members of the enzyme system synthesizing retinoic acid (especially during embryogenesis). They can oxidize some steroids and participate in bioamine and prostaglandin metabolism but so far the extent of their contribution to the latter processes is under discussion. Recent data suggest a correlation between the activity of ADH I in some organs and fine physiological processes including behavior regulation and craving for alcohol in albino rats.

Cytosolic and particulate monoamine oxidases have been isolated. Cytosolic preparation was free from mitochondrial and microsomal contaminations and also ribosome-bound MAO molecules. Cytosolic MAO had higher affinity for phenylethylamine and exhibited higher sensitivity to acetylenic inhibitors than the mitochondrial enzyme.

A series of pirlindole analogues were tested as inhibitors of monoamine oxidase A and B. Although we did not find strict dependence between 3D-size of molecules and their inhibitory potency, rigid analogues exhibited potent and selective inhibition of MAO-A. They have 3D size limits of 13 angstroms (length) x 7 angstroms (height) x 4.4 angstroms (widths). Besides MAO-A inhibition flexible analogues also demonstrated potent inhibition of MAO-B. Five compounds were studied as inhibitors of purified human liver MAO-A. Their inhibitory potencies coincided with those obtained using rat liver mitochondrial MAO-A. Each compound induced changes in the spectrum of MAO-A but these did not correlate with the flexibility of the derivative. It is also possible that the oxygen bridge introduced with the flexibility might influence spectral patterns.

A series of pyrazinocarbazoles, analogues of short acting antidepressant pirlindole (2,3,3a,4,5,6-hexahydro-8-methyl-1H-pyrazino[3,2,1-j,k]carbazole hydrochloride), were tested as inhibitors of monoamine oxidase A (MAO-A) and B (MAO-B). Rigid analogues exhibited potent and selective inhibition of MAO-A and have size limits (X:Y:Z) of 13.0 x 7.0 x 4.4 A. Besides MAO-A inhibition flexible analogues also demonstrated potent inhibition of MAO-B and in contrast to rigid analogues their inhibitory activity did not show the dependence on these sizes. The qualitative information (steric and electrostatic coefficients) from the 3D-QSAR with CoMFA models for MAO-A and -B are different, and this information can be used to determine the structural features influencing inhibitor selectivity.

Addition of 30mM glutamate to the culture medium decreased growth of rat glioma C6 cells accompanied by a decrease of DNA synthesis and an increase of lactate dehydrogenase (LDH) detected in the conditioned medium. The presence of 1 microM deprenyl attenuated the glutamate effect on cell growth only during the first 24-48 h incubation and had a minor influence on the glutamate-induced decrease of DNA synthesis. Clorgyline (1 microM) potentiated glutamate-induced DNA synthesis during the first 24 h incubation without significant influence on the cell growth. Deprenyl slightly attenuated the glutamate-induced LDH increase during 24 h incubation but potentiated the glutamate effect at 96 h. Clorgyline decreased the glutamate influence at 24 h and especially 96 h. All these effects were observed in the absence of exogenous monoamines in the culture medium. These results suggest that in transformed cells monoamine oxidase (MAO) inhibitors may influence processes of cell death via MAO-independent mechanisms.

The results of investigation concerning both total and cerebral catecholamine metabolism indices in 78 patients with amyotrophic lateral sclerosis (ALS) are presented. The considerable elevation of both blood and liquor norepinephrine level as well as of blood epinephrine concentration was observed together with acute decrease of platelet MAO B activity. The conclusion was made about the participation of catecholamines in exitotoxic mechanisms of motor neurons systems death which was quite characteristic for ALS development. A short literary review was presented concerning the role of neurotransmitters in regulation of motor functions. The neurochemical disturbances which may result in release of exitotoxic mechanisms of ALS were considered too. The consideration of data obtained as well as the analysis of modern conceptions of ALS pathogenesis enable both to determine some ways of ALS pathogenetic therapy and to define the basic directions of further investigations.

Indole and isatin (2,3-dioxindole) analogues were studied as inhibitors of MAO-A and B. They exhibited reversible and competitive MAO inhibition. Three dimensional structures of the compounds tested were constructed and minimized using PC-based molecular graphic software. The QSAR analysis revealed the requirement of co-planar structure of substituents at C2 and C3 of indole ring for selective MAO-A inhibition, whilst type of bond was less essential. The presence of hydroxy group at C5 of isatin increased selectivity of MAO-A inhibition, however simultaneous insertion of substituents into both positions of indole ring (5-hydroxy-2-phenylindole) led to a decrease of MAO-A inhibition. The planar molecules demonstrating potent MAO-A inhibition have the average sizes 7 A in length and 6 A in width. The MAO B inhibition also depended on the sizes of planar molecules however distribution of electron density in the molecules was another precondition for the selective inhibition of the enzyme.

The art-of-the-state and possible perspectives for studies of the properties of amine oxidases which are medically significant are briefly outlined. Due to the studies conducted at the Research Institute of Biomedical Chemistry of the Russian Academy of Medical Sciences, the authors discuss the results of studies of the following three problems: 1) modified catalytic properties of amine oxidases in experimental intoxications and abnormalities; 2) natural modulators of amine oxidases; 3) synthetic modulators of amine oxidases.

Langmuir-Blodgett (LB) films of monoamine oxidase (MAO) have been formed on the surface f a polypropylene membrane using amphiphilic polyelectrolytes. The enzyme activity of such protein-polyelectrolyte films was measured by a Clark electrodes. It was shown that in LB films thus formed the use of amphiphilc polyelectrolytes, MAO activity was higher than in polyelectrolyte-free LB films. Immobilization of MAO with branched polyethylenimine modified on 12% by laurylchain led to pronounced changes in its catalytic properties. The dependence of the enzyme's kinetic parameters on amphiphilic polyelectrolyte structures was discussed. (c) 1994 John Wiley & Sons, Inc.

The novel antidepressant tetrindole (2,3,3a,4,5,6-hexahydro-8-cyclohexyl-1H[3,2,1-j,k] carbazole) was found to be a selective inhibitor of monoamine oxidase A (MAO A). In vitro it inhibited rat brain mitochondrial MAO A in a competitive manner with Ki value of 0.4 microM. A 60 min preincubation did not change the competitive mode of interaction between enzyme and tetrindole (Ki value was 0.27 microM). The inhibition of rat brain mitochondrial MAO B was of mixed type with Ki value of 110 microM. Dilution or dialysis of mitochondrial suspension did not restore MAO A activity after inhibition by tetrindole both in vitro and in vivo, whereas inhibition of MAO B in vitro was completely reversible. Oral administration of tetrindole inhibited rat brain and liver mitochondrial MAO A by 80% within 0.5-1 hr and the onset of recovery of enzyme activity became evident after 24 hr. A small inhibition of MAO B (-20-30%) was observed in isolated brain and liver mitochondria within 1-6 hr and enzyme activity had completely recovered after 16 hr. The data obtained indicate that antidepressant activity of tetrindole may be explained by selective inhibition of MAO A, however an apparent discrepancy between competitive manner of MAO A inhibition in vitro and poor recovery of enzyme activity in vivo does not allow us to decide whether tetrindole is a "tight-binding" reversible inhibitor or a selective irreversible inhibitor of MAO A.

Effects of befol and moklobemide on thyramine-, serotonin- and 2-phenyl ethylamine deaminase activities of mitochondrial monoamine oxidase from bovine truncus cerebri were studied. These drugs are reversible noncompetitive inhibitors of the enzyme not requiring preincubation. They inhibited most effectively the serotonin deaminase activity as compared with phenyl ethylamine deaminase activity, however they should not be concerned with typical inhibitors of monoamine oxidases of the A type as inhibition of thyramine deaminase activity was not found.

The effect on deamination of serotonine, dopamine, tiramine and 2-phenylamine of benzamide derivatives befol, moclobemide and LIS-641 was studied. Befol and moclobemide are inhibitors of serotonine deaminating activity of MAO. The different sensitivity of this activity to the effect of the benzamide derivatives in beef or rat brain and human placenta was noted. The inhibition was more distinct in tissue homogenate than in corresponding mitochondrial fractions.

A bioluminescence assay is proposed for measuring monoamine oxidase activity in different biological specimens (platelets, mitochondria). The assay is based on the bioluminescent reaction catalysed by bacterial luciferase and coupled to monoamine oxidase. Two modifications of the bioluminescence assay were used. In the first case, the bioluminescent system was added to monoamine oxidase preincubated with the substrates, while in the second case, all the components of the coupled enzymatic systems were directly mixed in a cell. The proposed bioluminescence assay is simple, highly sensitive and rapid, and could be especially useful for biomedical examinations.

Multiplicity of platelet MAO was studied. Multiple forms of enzyme was separated with the use of 1.5% Tritone x-100 and, 1.3 M urea at pH 7.4 in, 0.01 M K-Na phosphate buffer. Three forms of MAO--MAO-I, MAO-II, and MAO-III were obtained under separation of solubilized proteins by affinity chromatography on AN-Sepharose 4B. Deprenyl in 10(-5) M inhibited all forms of the activity completely. Relation between multiple forms of the brain and platelet was discussed.

Treatment of normal human brain mitochondria with a mixture containing Triton X-100 and urea resulted in solubilization of monoamine oxidase (MAO) exhibiting tyramine-, serotonine-, phenylethylamine- and dopamine deaminase activities at ratios similar to those characteristic for the initial mitochondria. A purified preparation of the enzyme was obtained after AH-Sepharose chromatography; it was shown that in the brain there were present four isoenzymes of MAO possessing different substrate specificity. Investigation of some properties of MAO (activity, solubilization and isozyme composition) from brain regions showed absence of asymmetry and higher enzymatic activity in the subcortical brain region as compared with right and left brain cortex.

A highly purified individual form of monoamine oxidase (MAO-11b) has been isolated by means of affinity chromatography on AH-Sepharose 4B after solubilization of biomembranes from schizophrenic or normal brain tissues. The enzyme preparations obtained catalyzed deamination (both in schizophrenia and normal state) not only of serotonin and 2-phenylethylamine but also of histamine and contained about 2 SH-groups per 10(5) dalton of protein which is characteristic for "transformed" MAO with partially oxidized SH-groups. Preincubation of MAO-11b from normal brain with 10 mM dithiothreitol caused "re-transformation" of MAO: there was a marked decrease in histamine deaminating activity with simultaneous increase in the MAO activity and in content of SH-groups. In schizophrenia the re-transformation of MAO was impaired: preincubation of MAO-11b under the same conditions led to an increase in content of SH-groups and in MAO activity but the preincubation with a reducing agent did not decrease (causing, to the contrary, a marked increase) the deamination of histamine.

A total of 19 males with chronic idiopathic headache referred to in the literature as tension headache were examined. A secondary nature of headache was completely ruled out by additional studies. The activity of platelet monoamine oxidase was depressed to 14.33 +/- 1.17 n mol/mg of protein/h as compared with 28.1 +/- 2.38 n mol/mg of protein/h in the control group. The role of diminished activity of the enzyme in the genesis of headaches is considered.

The effect of different antidepressants (MAO inhibitors, monoamine uptake inhibitors, new drugs) on the activity of bovine brain monoamine oxidase was investigated. The type A MAO activity was found to be selectively inhibited by the morpholine derivative, moclobamide (IC50-10(-5) M). Pyrazidol, inkazan, imipramine, and iproniazide also had an inhibitory effect on the enzyme activity, but their action was not selective. Zymelidine and norzymelidine (10(-4) M) slightly reduced the deamination of serotonin and 2-phenylalanine. The hydrazine derivatives, N 33 and N 34 showed the same effects. The morpholine derivative, viloxazine had no effect on the MAO activity of bovine brain. It is inferred that not only classic MAO inhibitors but also antidepressants of different structure are capable of inhibiting brain monoamine oxidase.

The content of SH-groups and substrate specificity have been studied in purified preparations of monoamine oxidase (MAO) from human brain. It has been shown that both in schizophrenic and mentally normal persons MAO occurs in a partially oxidized state. The enzyme contains 2 SH-groups per 10(5) daltons of protein and deaminates MAO substrates (serotonin, beta-phenylethylamine) along with histamine, diamine oxidase substrate. Reduction of the partially oxidized SH-groups of MAO in schizophrenics up to 15 SH-groups per 10(5) daltons of protein (the normal value for human brain MAO) does not eliminate the histamine deaminase activity as is the case in experiments with MAO from the normal brain but, on the contrary, considerably potentiates it. The data suggest certain structural alteration of MAO in schizophrenia.

Mitochondrial monoamine oxidase isolated from bovine brain stem and purified to electrophoretic homogeneity contained 15 SH groups per mole (100000) of protein. The enzyme deaminated tyramine, p-nitro-beta-phenylethylamine, dopamine, 5-hydroxytryptamine, tryptamine but did not deaminate histamine, GABA or spermidine. Oxidation of 9-II SH groups in the MAO by air oxygen was accompanied by appearance of the properties to deaminate histamine or GABA. This qualitative alteration (transformation) in catalytic properties of the enzyme was readily reversed by treatment with reducing agents (dithiothreitol or GSH). No structural alterations detectable by electrophoresis in polyacrylamide gel were observed in course of the qualitative reversible modifications in catalytic activity of MAO. The qualitative alterations in substrate specificity were also initiated by treatment with H2O2 of the monoamine oxidases tightly bound with membrane structures of mitochondria from bovine brain stem.

The effect of 1-(beta-aminoethyl)-3H-pyrrole[2,3-h]quinoline (I), 3-(beta-aminoethyl)-1H-pyrrole[2,3-h]quinoline (I'), 8-amino-3H-pyrrole[2,3-h]quinoline (II), 6-amino-3H-pyrrole[2,3-h]quinoline (II') and 8-amino-1H-pyrrole[2,3-h]quinoline (III) on tyramine, serotonin and 2-phenylethylamine deaminase activities of mitochondrial monoamine oxidase from bovine brain were studied. All the compounds tested appeared to be reversibly inhibit MAO without preliminary incubation. Compounds II, II' and III specifically inhibited type A MAO; compound III exhibited the highest selectivity. The inhibition was of a mixed type. The effects of compounds I and I' were competitive and inconsistent with a classical concept on the dual activity of MAO, i. e., deamination of tyramine, a substrate common for MAO type A and MAO type B was inhibited in a greater degree than the deamination of specific substrates of MAO type A (serotonin) or type B (2-phenylethylamine). Possible reasons for the observed phenomenon are discussed.

Multiple forms of monoamine oxidase (MAO I, IIa, IIb, III) from bovine brain, separated by means of affinity chromatography on AH-Sepharose 4B, were dissimilar in kinetics of deamination of serotonin and beta-phenylethylamine used as substrates of the MAO of A and B types. MAO-I catalyzed the deamination of beta-phenyl ethylamine and serotonin. Km and Vmax values could not be calculated for MAO-IIa since the rate of enzymatic reactions was characterized by a complicated dependence on concentration of serotonin in a sample. MAO-IIb catalyzed also the deamination of both AMO substrates.

A method was developed for solubilization from bovine brain stem mitochondrial fraction of monoamine oxidases deminating biogenic amines. Preparative separation of the monoamine oxidases, possessing different substrate specificities, was achieved by column chromatography on a biospecific adsorbent AH-Sepharose 4 B. The enzyme preparations thus obtained did not contain any detectable by disc-electrophoresis of isoelectrofocusing in polyacrylamide gels proteins which were devoid of the monoamine oxidase activity.

Isopropylhydrazide of D,L-serine (IHS) inhibits by 50% (at 37 degrees for 10 min) deamination of serotonin or beta-phenylethylamine by monoamine oxidases from bovine brain stem mitochondrial membranes at the 2.6 X X 10(-5) M or 9 X 10(-5) M, respectively. In order to inhibit by 50% the deamination of tyramine under the same conditions a considerably lower (2.5 X X 10(-6) M) concentration of IHS is required. Kinetic studies of inhibition of enzymatic deamination of all the three biogenic monoamines by IHS showed that the irreversible blocking of the monoamine oxidase activity is preceeded by formation of dissociating enzyme-inhibitor complexes. Values of the dissociation constants of these complexes measured (at 37 degrees) with serotonin, phenylethylamine or tyramine as substrates for estimation of the residual monoamine oxidase activity are 0.47; 0.13 or 0.023 mM, respectively. Significant differences are also found between thermodynamic and activation parameters characterizing both both steps of interaction between IHS and the monoamine oxidases of mitochondrial membranes in the experiments with serotonin, phenylethylamine or tyramine as substrates. The data obtained suggest the existence of different monoamine oxidases (or their active sites) catalyzing oxidative deamination of serotonin, phenylethylamine or tyramine in the fragments of mitochondrial membranes from bovine brain stem.

Anti-norepinephrine deaminative activity of some antidepressants of different structure was studied. Pyrazidol (10(-5) M) reduced considerably the rate of norepinephrine deamination in bovine brain (80% inhibition), the inhibitory effects of inkazan and imipramine were also apparent (50-60%). Zimelidine, viloxazine and norzimelidine were found to be less active: at 10(-4) M, they caused a not more than 50% inhibition of oxidative norepinephrine deamination. The difference was revealed between the influence of some drugs on deamination of two monoamine oxidase A substrates: norepinephrine and serotonin. Thus, pyrazidol, viloxazine, zimelidine and norzimelidine were more active in suppressing norepinephrine, than serotonin deamination. Inhibition of norepinephrine deamination in the brain seems to be an important component of the neurochemical spectrum of pyrazidol and imipramine.