Investigation of the oxygenation of phospholipids by the porcine leukocyte and human platelet arachidonate 12-lipoxygenases.
When arachidonate 12-lipoxygenase purified from porcine leukocytes was incubated aerobically with 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, the phospholipid reacted at up to 30% of the rate of a free fatty acid substrate; the esterified arachidonic acid was oxygenated predominantly to the (12S)-12-hydroperoxy product. The porcine leukocyte enzyme was also capable of metabolizing phosphatidylcholine containing esterified (15S)-15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; oxygenation occurred predominantly at the 14R position. Reaction with mitochondrial and endoplasmic membranes of rat liver produced esterified (12S)-12-hydroperoxy-5,8,10,14-eicosatetraenoic acid and (13S)-13-hydroperoxy-9,11-octadecadienoic acid as major oxygenation products. Thus, porcine leukocyte 12-lipoxygenase is capable of oxygenating not only free polyenoic fatty acids but also more complex substrates such as phospholipids and biomembranes. In contrast, the human platelet 12-lipoxygenase is almost inactive with these esterified polyenoic fatty acids. In regard to the function of these enzymes, the leukocyte-type of 12-lipoxygenase has similar catalytic activities to the mammalian 15-lipoxygenase and its physiological function may include the structural modification of membrane lipids.
Takahashi
Y
Y
Department of Biochemistry, Tokushima University School of Medicine, Japan.
Glasgow
W C
WC
Suzuki
H
H
Taketani
Y
Y
Yamamoto
S
S
Anton
M
M
Kühn
H
H
Brash
A R
AR
D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism*; D001792:Blood Platelets / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007700:Kinetics; D007962:Leukocytes / Q000201:enzymology*; D008563:Membrane Lipids / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D051381:Rats; D013552:Swine
D008563:Membrane Lipids; D010743:Phospholipids; D001092:Arachidonate 12-Lipoxygenase; D010100:Oxygen