Modification of substrate-inhibitor affinities of human platelet monoamine oxidase B in vitro.
The rate of benzylamine utilization by monoamine oxidase (MAO)-B from human blood platelets was 2-4 times higher than that for octopamine. Both activities were inhibited 100% by 10(-7) M deprenyl (a specific MAO-B inhibitor) and were not affected by clorgyline (a specific MAO-A inhibitor) or by polyclonal antibodies to MAO-A. The preincubation of platelet MAO-B with purified MAO-A from mitochondrial membranes of human placenta resulted in appearance of excess octopamine activity. This additional activity was not precipitated by antibodies to MAO-A or inhibited by deprenyl but was inhibited by clorgyline. Incubation of the MAO-A preparation from placenta at 45 degrees C for 15 min before its preincubation with MAO-B caused 50% loss of both activities. Protease inhibitors had no effect on the modification of MAO. These data indicate that MAO-A or a factor tightly bound to it can modify MAO-B yielding a form of the enzyme with both MAO-A and MAO-B substrate and inhibitor affinities and MAO-B immunospecificity.
Szutowicz
A
A
Department of Clinical Biochemistry, Medical Academy, Gdańsk, Poland.
Tomaszewicz
M
M
Orsulak
P J
PJ
D000906:Antibodies; D000936:Antigen-Antibody Complex / Q000032:analysis; D001596:Benzylamines / Q000378:metabolism; D001792:Blood Platelets / Q000201:enzymology*; D003010:Clorgyline / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000097:blood* / Q000276:immunology / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D008995:Monoamine Oxidase / Q000097:blood* / Q000276:immunology / Q000378:metabolism; D009655:Octopamine / Q000378:metabolism; D010627:Phenethylamines / Q000494:pharmacology*; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D011437:Propylamines / Q000494:pharmacology*; D012642:Selegiline / Q000494:pharmacology*; D013379:Substrate Specificity; D013816:Thermodynamics
D000906:Antibodies; D000936:Antigen-Antibody Complex; D001596:Benzylamines; D007527:Isoenzymes; D010627:Phenethylamines; D011437:Propylamines; D009655:Octopamine; D012642:Selegiline; C030796:benzylamine; D008995:Monoamine Oxidase; D003010:Clorgyline