Arai H, Suzuki T, Takama K, Terao J
Department of Marine Bioresources Chemistry, Faculty of Fisheries, Hokkaido University, Japan.
Biochem Biophys Res Commun. 1996 Nov 21;228(3):675-82. doi: 10.1006/bbrc.1996.1716.
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.
通过测量大单层脂质体（LUV）悬浮液中的氧气摄取，研究了兔网织红细胞15-脂氧合酶（15-LOX）与含有亚油酸（LA-PC）、花生四烯酸（AA-PC）或二十二碳六烯酸（DHA-PC）的磷脂酰胆碱（PC）的反应活性。发现15-LOX与PC LUV的反应遵循米氏动力学。LA-PC、AA-PC和DHA-PC的LUV的米氏常数（K(m)）的表观值几乎相同（1.0 - 1.2 mM）。然而，DHA-PC的最大速度（Vmax）明显比LA-PC和AA-PC低两到三倍。另一方面，在LUV的自由基链反应中，不饱和脂肪酸每两个烯丙基氢的PC的氧化能力随着不饱和度的增加而降低，即LA-PC > AA-PC > DHA-PC。这些结果表明，在脂氧合酶反应中，掺入生物膜的DHA部分的氧化能力不一定像在自由基链反应中那样高。
