Is ATP a substrate for 15-lipoxygenase?
Lipoxygenases catalyze peroxidation of polyunsaturated fatty acids containing the 1-cis, 4-cis pentadiene structure. Linoleic (18:2), linolenic (18:3), and arachidonic (20:4) acids are the predominant substrates for this class of enzymes. Effects of 15-lipoxygenase on the hydrolysis of adenosine 5'-triphosphate were investigated in vitro using soybean lipoxygenase and adenosine 5'-[gamma-32P]triphosphate. The amount of inorganic phosphate released from adenosine 5'-triphosphate was dependent upon enzyme as well as substrate concentrations, pH, and the duration of incubation. The ATPase activity with a Vmax value of 3.3 mumol.mg protein-1.h-1 and a Km value of 5.9 mM was noted in the presence of different concentrations of ATP at pH = 7.4. Phenidone, a lipoxygenase inhibitor, had no effect on this reaction. These findings suggest that soybean lipoxygenase catalyzes the release of inorganic phosphate from ATP primarily via hydrolysis.
Kumarathasan
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Hypertension Unit, University of Ottawa Heart Institute, ON, Canada.
Leenen
F H
FH
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D006736:Horses; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D013025:Glycine max / Q000201:enzymology; D013379:Substrate Specificity; D013997:Time Factors
D005231:Fatty Acids, Unsaturated; D016859:Lipoxygenase Inhibitors; D010710:Phosphates; D011720:Pyrazoles; D000255:Adenosine Triphosphate; D001093:Arachidonate 15-Lipoxygenase; C015429:phenidone