کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1925141 | 1536346 | 2014 | 7 صفحه PDF | دانلود رایگان |
• The prototype lipoxygenases (LOX) with catalytic Fe and Mn were compared.
• Soybean LOX-1 (sLOX-1) showed a large kinetic deuterium isotope effect.
• The prominent kinetic deuterium isotope effect of MnLOX was temperature-dependent.
• This difference to sLOX-1 could be due to protein dynamics and the catalytic metals.
Lipoxygenases (LOX) oxidize polyunsaturated fatty acids to hydroperoxides, which are generated by proton coupled electron transfer to the metal center with FeIIIOH− or MnIIIOH−. Hydrogen abstraction by FeIIIOH− of soybean LOX-1 (sLOX-1) is associated with a large deuterium kinetic isotope effect (D-KIE). Our goal was to compare the D-KIE and other kinetic parameters at different temperatures of sLOX-1 with 13R-LOX with catalytic manganese (13R-MnLOX). The reaction rate and the D-KIE of sLOX-1 with unlabeled and [11-2H2]18:2n-6 were almost temperature independent with an apparent D-KIE of ∼56 at 30 °C, which is in agreement with previous studies. In contrast, the reaction rate of 13R-MnLOX increased 7-fold with temperature (8–50 °C), and the apparent D-KIE decreased linearly from ∼38 at 8 °C to ∼20 at 50 °C. The kinetic lag phase of 13R-MnLOX was consistently extended at low temperatures. The Phe337Ile mutant of 13R-MnLOX, which catalyzes antarafacial hydrogen abstraction and oxygenation in analogy with sLOX-1, retained the large D-KIE and its temperature-dependent reaction rate. The kinetic differences between13R-MnLOX and sLOX-1 may be due to protein dynamics, hydrogen donor–acceptor distances, and to the metal ligands, which may not equalize the 0.7 V-gap between the redox potentials of the free metals.
Journal: Archives of Biochemistry and Biophysics - Volumes 555–556, August 2014, Pages 9–15