title: Reactivity of mammalian 15-lipoxygenase with phospholipids in large unilamellar liposomes.
abstract: The reactivity of rabbit reticulocyte 15-lipoxygenase (15-LOX) with phosphatidylcholine (PC) possessing linoleic acid (LA-PC), arachidonic acid (AA-PC), or docosahexaenoic acid (DHA-PC) was investigated by measuring oxygen uptake in the suspension of large unilamellar liposomes (LUV). The 15-LOX reaction with PC LUV was found to follow Michaelis-Menten kinetics. The apparent values of the Michaelis constants (K(m)) of LUV of LA-PC, AA-PC, and DHA-PC were nearly the same (1.0-1.2 mM). However, the maximum velocity (Vmax) of DHA-PC was obviously two to three times lower than those of LA-PC and AA-PC. On the other hand, the oxidizability of PC per bis-allylic H of unsaturated fatty acids in the free radical chain reaction of LUV decreased with increasing degree of unsaturation, that is, LA-PC > AA-PC > DHA-PC. These results suggested that the oxidizability of the DHA moiety incorporated into biomembranes is not necessarily high in lipoxygenase reaction as in free radical chain reaction.
authors.affiliation: Department of Marine Bioresources Chemistry, Faculty of Fisheries, Hokkaido University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Arai
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Takama
authors.forename: J
authors.initials: J
authors.lastname: Terao
mesh_terms: D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D008081:Liposomes; D010713:Phosphatidylcholines; D001093:Arachidonate 15-Lipoxygenase