title: [Comparative characteristics of membrane bound and cytoplasmic monoamine oxidases in human placenta].
abstract: Catalytic and physico-chemical properties of human placental monoamine oxidases (MAO) were studied. Both forms of the enzyme, membrane-bound and soluble, exhibited similar properties: optimal activity at pH8.3, equal rate of inhibition with selective MAO inhibitors, identical substrate specificity (the best substrate--serotonin). Some specific differences were found only for cytoplasmic (soluble) MAO: lower affinity for substrates as compared with membrane-bound enzymes, reversible interaction with an inhibitor Lilly 51641 even after long-term preincubation, whereas the mitochondrial MAO bound Lilly 51641 irreversibly. The property of cytoplasmic MAO to form aggregates during storage and/or in gel filtration and concentration did not affect the main catalytic properties of soluble enzyme. Analysis of isoenzyme spectra of membrane-bound and cytoplasmic MAO by means of selective inhibitors and electrophoresis showed that MAO of the two types--A and B were detected in all the subcellular fractions studied. Subunits of MAO of the A type had molecular masses 62, 61 and 61 kDa and of MAO of the B type--51, 55 and 55 kDa in mitochondria, microsomes and cytosol, respectively.
authors.forename: A Z
authors.initials: AZ
authors.lastname: Kirkel'
authors.forename: L A
authors.initials: LA
authors.lastname: Tishchenko
authors.forename: L N
authors.initials: LN
authors.lastname: Aksenova
authors.forename: V A
authors.initials: VA
authors.lastname: Pekkel'
authors.forename: V Z
authors.initials: VZ
authors.lastname: Gorkin
mesh_terms: D002384:Catalysis; D002462:Cell Membrane / Q000201:enzymology; D002850:Chromatography, Gel; D003593:Cytoplasm / Q000201:enzymology; D005260:Female; D006801:Humans; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D008995:Monoamine Oxidase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010627:Phenethylamines / Q000037:antagonists & inhibitors / Q000378:metabolism; D010920:Placenta / Q000201:enzymology*; D012701:Serotonin / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D010627:Phenethylamines; C029261:phenethylamine; D012701:Serotonin; D008995:Monoamine Oxidase
vernacular_title: Sravnitel'naia kharakteristika membranno-sviazannykh i tsitoplazmaticheskoĭ monoaminoksidaz platsenty cheloveka.