Positional specificity of a Lupinus albus lipoxygenase in relation to enzyme concentration and effect of a double dioxygenation product of arachidonic acid.
When arachidonic acid was incubated with Lupinus Albus lipoxygenase, a trienoic fatty acid, 8,15-dihydroperoxy-5,9,11,13-eicosatetraenoic acid was formed in addition to the three HPETEs, 15-HPETE, 8-HPETE and 5-HPETE. The formation of the two major monohydroperoxy acids (15- and 5-HPETE) has been shown to depend on enzyme concentration. At low enzyme concentration (less than or equal to 1 unit), Lupinus Albus lipoxygenase displays its highest regiospecificity at pH 5.8, resulting in the formation of 5-HPETE as the major product (80%). As the enzyme concentration increased, the proportion of 5-HPETE decreased, while the one of 15-HPETE increased. On the other hand, the preincubation of the enzyme with 8,15-diHPETE led to the gradual inactivation of the lipoxygenase activity. The inhibitory effect of 8,15-diHPETE was abolished by using high enzyme concentration. Based on these observations, it is proposed that the trienoic fatty acid, 8,15-diHPETE stemmed from further lipoxygenation of 15-HPETE, blocked the formation of the 15(S) hydroperoxide by Lupinus Albus lipoxygenase but not the formation of 5(S) hydroperoxide.
Andrianarison
R H
RH
Laboratoire de Biochimie, Faculté de Pharmacie, Limoges, France.
Tixier
M
M
Beneytout
J L
JL
D001095:Arachidonic Acids / Q000378:metabolism*; D004789:Enzyme Activation; D006861:Hydrogen Peroxide / Q000378:metabolism; D015289:Leukotrienes / Q000378:metabolism*; D008054:Lipid Peroxides / Q000378:metabolism*; D008084:Lipoxygenase / Q000378:metabolism; D010944:Plants / Q000201:enzymology*; D012639:Seeds / Q000201:enzymology; D013379:Substrate Specificity
D001095:Arachidonic Acids; D015289:Leukotrienes; D008054:Lipid Peroxides; C053262:8,15-diHPETE; C025086:15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; D006861:Hydrogen Peroxide; D008084:Lipoxygenase