Deutsches Krebsforschungszentrum 
German Cancer Resarch CenterLOX-DB - LipOXygenases DataBase
Lipoxygenases...
What are Lipoxygenases?
Lipoxygenases and
cancer research
Database...
Search
Display all entries
Alignments
Sequence Comparison
Blast Search
Search Literature
Search Literature (adv.)
Misc...
Image Gallery
Links
Forum
Contact
Guestbook
Home

LOX-DB - Literature


Kinetics of manganese lipoxygenase with a catalytic mononuclear redox center.

Su C, Sahlin M, Oliw EH

J Biol Chem 275: 18830-18835 (2000)

Abstract:

Manganese lipoxygenase was isolated from the take-all fungus, Gaeumannomyces graminis, and the oxygenation mechanism was investigated. A kinetic isotope effect, k(H)/k(D) = 21-24, was observed with [U-(2)H]linoleic acid as a substrate. The relative biosynthesis of (11S)-hydroperoxylinoleate (11S-HPODE) and (13R)-hydroperoxylinoleate (13R-HPODE) was pH-dependent and changed by [U-(2)H]linoleic acid. Stopped-flow kinetic traces of linoleic and alpha-linolenic acids indicated catalytic lag times of approximately 45 ms, which were followed by bursts of enzyme activity for approximately 60 ms and then by steady state (k(cat) approximately 26 and approximately 47 s(-1), respectively). 11S-HPODE was isomerized by manganese lipoxygenase to 13R-HPODE and formed from linoleic acid at the same rates (k(cat) 7-9 s(-1)). Catalysis was accompanied by collisional quenching of the long wavelength fluorescence (640-685 nm) by fatty acid substrates and 13R-HPODE. Electron paramagnetic resonance (EPR) of native manganese lipoxygenase showed weak 6-fold hyperfine splitting superimposed on a broad resonance indicating two populations of Mn(II) bound to protein. The addition of linoleic acid decreased both components, and denaturation of the lipoxygenase liberated approximately 0.8 Mn(2+) atoms/lipoxygenase molecule. These observations are consistent with a mononuclear Mn(II) center in the native state, which is converted during catalysis to an EPR silent Mn(III) state. We propose that manganese lipoxygenase has kinetic and redox properties similar to iron lipoxygenases.

LOX-DB entries related to this article: manganese_lox