title: Effects of soybean lipoxygenase on Na+/K+-ATPase activity in vitro.
abstract: Oxidized metabolites of polyunsaturated fatty acids produced by lipoxygenase are among the endogenous regulators of Na+/K+-ATPase. The direct effect of lipoxygenase on Na+/K+-ATPase activity was assessed in vitro using soybean lipoxygenase. Treatment of 4.2 microg/mL Na+/K+-ATPase (from dog kidneys) with 4.2 microg/mL of soybean lipoxygenase caused 20+/-2% inhibition of ATPase activity. A 10-fold increase in lipoxygenase concentration (41.6 microg/mL) led to 30+/-0.3% inhibition. In the presence of 12 microg/mL phenidone (a lipoxygenase inhibitor) and 15.4 microg/mL glutathione (a tripeptide containing a cysteine residue) inhibition of Na+/K+-ATPase activity was blocked and an increase in ATPase activity was observed. The presence of lipoxygenase enhanced the inhibition of Na+/K+-ATPase activity caused by 20 ng/mL ouabain (31+/-2 vs. 19+/-2) but had little or no effect with higher concentrations of ouabain. These findings suggest that lipoxygenase may regulate Na+/K+-ATPase by acting directly on the enzyme.
authors.affiliation: Hypertension Unit, University of Ottawa Heart Institute, University of Ottawa, ON, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Kumarathasan
authors.forename: F H
authors.initials: FH
authors.lastname: Leenen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000494:pharmacology*; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D030262:Soybean Proteins / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D016859:Lipoxygenase Inhibitors; D030262:Soybean Proteins; D010042:Ouabain; D000255:Adenosine Triphosphate; D001093:Arachidonate 15-Lipoxygenase; D000254:Sodium-Potassium-Exchanging ATPase; D005978:Glutathione