Interaction of dopamine-beta-monooxygenase with lipids: 1. Lipids as modulators of the catalytic activity of the enzyme.
The interaction of the membrane-bound and soluble forms of dopamine-beta-monooxygenase with a variety of lipid analogues of the membrane of chromaffin granules were studied. The use of two independent methods to determine the kinetics of product formation and of oxidation of the electron donor substrates (two substrates, dopamine and tyramine, and two electron donors, ascorbate and ferrocyanide), showed that the enzyme is activated in the presence of either phosphatidylcholine or lysophosphatidylcholine, but is inhibited by phosphatidylserine, phosphatidylethanolamine, and phosphatidic acid. The magnitude of the effects observed was the same for both forms of the enzyme. The parameters Vmax and Km for the substrates and for the electron donors were determined in the presence of each of the lipids tested. The data lead to certain conclusions about the mechanism of action of the lipids upon the enzyme and about the possible physiological role of the effects observed.
Boyadzhyan
A S
AS
Institute of Experimental Biology, Academy of Sciences of the Armenian SSR, Erevan.
Karagezyan
K G
KG
D000818:Animals; D002384:Catalysis / Q000187:drug effects; D002417:Cattle; D002837:Chromaffin Granules / Q000201:enzymology; D004299:Dopamine beta-Hydroxylase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008055:Lipids / Q000494:pharmacology*; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction
D008055:Lipids; D008565:Membrane Proteins; D004299:Dopamine beta-Hydroxylase