I. N. Basova

Comparative sensitivity of liver monoamine oxidases of frog and whitefish to some tricyclic compounds

There is performed a comparative analysis of action of four acridine derivatives and of one xanthene derivative (pyronin G) on activity of liver monoamine oxidase (MAO) of two species of poikilothermal freshwater animals: a representative of amphibians—the common frog Rana temporaria and a representative of the Salmonidae order—the European whitefish Coregonus lavaretus. The studied synthetic hexamember tricyclic compounds show the irreversible character of inhibition of intermediate potency towards the enzyme from the both biological sources. There are obtained qualitative and quantitative differences in the reaction ability and selectivity of action of the studied inhibitors for liver MAO of frog and whitefish. The obtained data of the inhibitory analysis with use of specific substrates are an indirect proof for the existence in liver of the studies frog species of two molecular forms, whereas in the whitefish liver—the single molecular MAO form.

Liver monoamine oxidase activity of the lamprey Lampetra fluviatilis . The substrate-inhibitor specificity

Based on the data of substrate-inhibitor analysis with the use of specific inhibitors-deprenyl, chlorgilin, and specific substrates-serotonin, noradrenalin, benzylamine, β-phenylethylamine and N-methylhistamine, one molecular form of monoamine oxidase (MAO) was suggested to possibly exist in liver of mature individuals of the European lamprey Lampetra fluviatilis. The kinetic parameters of monoamine oxidase deamination of eight substrates were determined, which indicates the large spectrum of substrate specificity of MAO from the lamprey liver. The studied enzyme does not deaminate histamine and putrescine and is not sensitive to 10−2 M semicarbaside. Results of the study of the substrate-inhibitor specificity allow us to suggest some resemblance in catalytic properties of the lamprey liver MAO and the mammalian MAO of the form A. The low activity of the enzyme revealed at deamination of all used substrates seems to be associated with low detoxifying function of the lamprey liver.

Substrate-inhibitory analysis of monoamine oxidase from hepatopancreas of the octopus Bathypolypus arcticus

Study of the substrate-inhibitory specificity of mitochondrial monoamine oxidase (MAO) of hepatopancreas of the octopus Bathypolypus arcticus revealed distinctive peculiarities of catalytic properties of this enzyme. The studied enzyme, on one hand, like the classic MAO of homoiothermal animals, is able to deaminate tyramine, serotonin, benzylamine, tryptamine, b-phenylethylamine, while, on the other hand, it deaminates histamine and does not deaminate putrescine-classic substrates of diamine oxidase (DAO). Results of the substrate-inhibitory analysis with use of chlorgiline and deprenyl are indirect proofs for the existence in the octopus hepatopancreas of one molecular MAO form. Semicarbazide and pyronine G turned out to be weak irreversible inhibitors, four derivatives of acridine-irreversible inhibitors of the intermediate effectiveness with respect to the octopus hepatopancreas MAO; specificity of action of inhibitors at deamination of different substrates was equal.

Comparative study of inhibitory specificity of liver monoamine oxidase in frogs Rana ridibunda and Rana temporaria

A comparative enzymological investigation of inhibitory specificity of the liver monoamine oxidases (MAO) from the two frog species, lake frog Rana ridibunda and grass frog Rana temporaria, revealed certain interspecies similarities and distinctions of this enzyme. The anti-monoamine oxidase effect of five derivatives of acridine, three derivatives of phenothiazine and one derivative of xanthene (pyronine G) was comparatively analyzed. The tested six-membered tricyclic compounds were shown to exert an irreversible inhibitory effect on the enzyme from both biological sources, displaying the same substrate deamination specificity. Thus, the rate of interaction of acridine and phenothiazine derivatives with the MAO active center in both frog species was considerably higher when activity was determined using noradrenaline versus N-methylhistamine, while that of pyronine G—when activity was determined using N-methylhistamine versus noradrenaline. Interspecies quantitative differences were found in the inhibitory efficacy and degree of selectivity of the tested tricyclic compounds, indicative of the differences in catalytic properties of liver MAO at the interspecies level in the representatives of the genus Rana, family Ranidae. The data of substratespecific inhibitory analysis provide indirect evidence of the existence of two molecular MAO forms in the liver of the studied frog species.

Catalytic properties of liver monoamine oxidase in the chum salmon Oncorhynchus keta

The substrate and inhibitory specificity of mitochondrial monoamine oxidase (MAO) was studied in the summer-run male chum salmon Oncorhynchus keta liver. By the spectrum of deaminated substrates, chum salmon liver MAO is similar to that in most terrestrial mammals, with similarities in substrate characteristics found for eight classical MAO substrates. An assay of anti-monoamine oxidase efficacy of the two 2-propinilamine derivatives, five acridine derivatives and pyronine G revealed significant qualitative and quantitative differences as compared with tuna and whitefish liver MAO. The compounds tested were found to be irreversible inhibitors of chum salmon liver MAO exhibiting various efficacy, but lacking selectivity dependening on a deaminated substrate. The data of substrate–inhibitory analysis provide indirect evidence for the presence of a single molecular MAO form in the chum salmon liver.

Sensitivity of Liver Monoamine Oxidase in the Lamprey Lampetra fluviatilis to Some Tricyclic Compounds

A comparative analysis of the effect of the five acridine, three phenothiazine and one xanten (pyronine G) derivatives on the activity of liver mitochondrial monoamine oxidase (MAO) in sexually mature male river lampreys Lampetra fluviatilis has been conducted. Tyramine, dopamine, serotonin, noradrenaline, benzylamine, ß-phenylethylamine and N-methylhistamine have been used as substrates for analyzing the monoamine oxidase activity of heterocyclic compounds. The analyzed synthetic hexamerous tricyclic compounds exhibit irreversible inhibition of the enzyme but no specificity depending on the desaminated substrate. The number and identity of heteroatoms in the analyzed heterocyclic compounds have been established to influence their inhibitory efficiency. The data of substrate-inhibitory analysis obtained with the use of the specific substrates provide indirect evidence for the existence of a single MAO form in the lamprey liver.

Comparative enzymologic study of catalytical properties of liver monoamine oxidases of sturgeon fish

We carried out the comparative study of the substrate and inhibitory specificity of liver monoamine oxidases (MAO) of the giant sturgeon Huso huso, the starred sturgeon Acipenser stellatus, the Persian sturgeon Acipenser persicus, and the Russian sturgeon Acipenser gueldenstaedtii. Results of the substrate-inhibitor analysis with use of inhibitors chlorgilin and deprenil, as well as five specific substrates indicate homogeneity of these enzymes. All studied MAO have the several orders higher sensitivity to chlorgilin than to deprenil, with essential interspecies differences being observed. There are determined kinetic parameters of enzymatic deamination (KM and V) of tyramine, serotonin, noradrenalin, benzylamine, β-phenylethylamine, and N-methylhistamine. All studied enzymes have been established to have the higher activity toward serotonin and noradrenalin-substrates of the MAO A form as compared with benzylamine, β-phenylethylamine, and N-methylhistamine-substrate of the mammalian MAO B form, the maximal activity being characteristic of the giant sturgeon.

Reactivity of liver monoamine oxidase in the seal Phoca hispida ladogensis

The goal of this work consisted in substrate and inhibitor specificity of liver monoamine oxidase (MAO) of the freshwater Ladoga subspecies of the ringed seal Phoca hispida ladogensis. The studied enzyme has been found to have the large substrate specificity by deaminating, apart from eight classic substrates of the terrestrial mammalian MAO, also histamine, the substrate of diamino oxidase. It has been revealed that the studied enzyme realizes wide substrate specificity by deaminating, apart from eight classic MAO substrates of terrestrial mammals, also histamine, the substrate of diamino oxidase. The deamination rates of benzylamine, β-phenylethylamine, and N-methylhistamine are found to be almost by one order higher than the deamination rates of serotonin and noradrenaline. The seal liver MAO did not deaminate putrescine and cadaverine and was insensitive to 10−2 M semicarbaside. There were calculated bimolecular rate constants of interaction of inhibitors: chlorgyline, deprenyl, berberine, sanguinarine, chelidonine, and four derivatives of acridine with the enzyme at deamination of nine substrates. By the method of substrate-inhibitor analysis we have shown heterogeneity of the enzyme, i.e., the presence in the seal liver of at least of two different MAO.

Enzymologic Characteristics of Monoamine Oxidase from Liver of the Skipjack Tuna Katsuwonus pelamis

Substrate and inhibitory specificity of mitochondrial monoamine oxidase (MAO) from liver of skipjack tuna Katsuwonus pelamis was studied. The results of substrate—inhibitory analysis with application of chlorgilin and deprenyl might be indirect proofs of existence of one molecular MAO form in the tuna liver. Studied enzyme, as liver MAO of terrestrial mammals, deaminates tyramine, tryptamine, dopamine, serotonin, noradrenalin, benzylamine, β-phenylethylamine, N-methylhistamine and does not deaminate histamine, is not suppressed by 10 mM semicarbazide. Takrin, acriflavin, proflavin, acridine orange and pyronine G were established to be irreversible inhibitors of middle strength in respect to MAO of tuna liver. The specificity of inhibitors action upon deamination of various substrates was equal.

Catalytic characteristics of monoamine oxidase of whitefish Coregonus lavaretus ludoga

Study of substrate-inhibitory specificity of liver mitochondrial monoamine oxidase (MAO) of adult individuals of the whitefish Coregonus lavaretus ludoga P. from the Ladoga Lake has revealed distinguished peculiarities of catalytic properties of this enzyme. The studied MAO, on one hand, like the classical enzyme of homoiothermal animals, is able to deaminate tyramine, serotonin, benzylamine, tryptamine, and β-phenylalanine, but, on the other hand, to deaminate histamine, the classic substrate of diamine oxidase. The found equal activity and sorptional ability of the enzyme toward six studied substrates including histamine, as well as results of the substrate-inhibitory analysis with use of specific inhibitors-deprenyl and chlorgilin-indicate homogeneity of the enzyme. The detected for the first time among the fish MAO wide substrate specificity and an unusually low sensitivity to both studied acetylene inhibitors does not allow ascribing unanimously the studied enzyme to the MAO forms known in organs and tissues of homoiothermal organisms. Apparently, the revealed enzyme form of this poikilothermal organism is not the true MAO, but performs a large amine oxidase function.