TY - JOUR
T1 - Oxidation of linoleyl alcohol by potato tuber lipoxygenase
T2 - Kinetics and positional, stereo, and geometrical (cis, trans) specificity of the reaction
AU - Butovich, I. A.
AU - Luk'Yanova, S. M.
AU - Reddy, C. Channa
PY - 2000/6/1
Y1 - 2000/6/1
N2 - The dioxygenation of linoleyl alcohol (LAL) by potato tuber lipoxygenase leads to formation of two positional isomeric products - 9- and 13- hydroperoxyoctadecadien-1-ols (Butovich, I. A., Luk'yanova, S. M., and Reddy, C. C. (1998) Biochem. Biophys. Res. Commun. 249, 344-349). In the present study, we examined the stereospecificity and double-bond conformation of primary dioxygenation products of LAL catalyzed by potato lipoxygenase. In contrast to the product profiles of linoleic acid oxidation by potato lipoxygenase, oxidation of LAL led to all possible positional (9- and 13-), stereo, and geometrical (cis,trans and all-trans) isomers in equimolar mixtures at 25°C. The reaction appears to proceed through an enzyme- catalyzed formation of a pentadiene carbon-centered radical followed by resonance stabilization of the radical and molecular oxygen insertion in an enzyme-dependent as well as an enzyme-independent pathway. A strict positional, stereo, and geometrical specificity of the dioxygenation products of LAL oxidation appears to be maintained when the reaction occurs at the active site of the enzyme. However, when the pentadiene carbon-centered radical of LAL is dissociated from the active site of the enzyme, it appears to be nonenzymatically transformed into a mixture of all possible positional and geometrical stereoisomers of primary dioxygenation products. The latter pathway was effectively blocked by the free radical scavenger 4-hydroxy- TEMPO, which substantially reduced the production of all-trans hydroperoxyoctadecadienols. In the presence of the scavenger, 9(S)- hydroperoxy-10E, 12Z-octadecadien-1-ol was the predominant LAL oxidation product, representing approximately 80% of the total conjugated dienes, with 13(S)-hydroxy-9Z, 11E-octadecadien-1-ol the expected product of reverse orientation of the substrate at the active site, accounting for approximately 10%. A similar pattern in oxidation of LAL was observed when the reactions were carried out at 0°C. (C) 2000 Academic Press.
AB - The dioxygenation of linoleyl alcohol (LAL) by potato tuber lipoxygenase leads to formation of two positional isomeric products - 9- and 13- hydroperoxyoctadecadien-1-ols (Butovich, I. A., Luk'yanova, S. M., and Reddy, C. C. (1998) Biochem. Biophys. Res. Commun. 249, 344-349). In the present study, we examined the stereospecificity and double-bond conformation of primary dioxygenation products of LAL catalyzed by potato lipoxygenase. In contrast to the product profiles of linoleic acid oxidation by potato lipoxygenase, oxidation of LAL led to all possible positional (9- and 13-), stereo, and geometrical (cis,trans and all-trans) isomers in equimolar mixtures at 25°C. The reaction appears to proceed through an enzyme- catalyzed formation of a pentadiene carbon-centered radical followed by resonance stabilization of the radical and molecular oxygen insertion in an enzyme-dependent as well as an enzyme-independent pathway. A strict positional, stereo, and geometrical specificity of the dioxygenation products of LAL oxidation appears to be maintained when the reaction occurs at the active site of the enzyme. However, when the pentadiene carbon-centered radical of LAL is dissociated from the active site of the enzyme, it appears to be nonenzymatically transformed into a mixture of all possible positional and geometrical stereoisomers of primary dioxygenation products. The latter pathway was effectively blocked by the free radical scavenger 4-hydroxy- TEMPO, which substantially reduced the production of all-trans hydroperoxyoctadecadienols. In the presence of the scavenger, 9(S)- hydroperoxy-10E, 12Z-octadecadien-1-ol was the predominant LAL oxidation product, representing approximately 80% of the total conjugated dienes, with 13(S)-hydroxy-9Z, 11E-octadecadien-1-ol the expected product of reverse orientation of the substrate at the active site, accounting for approximately 10%. A similar pattern in oxidation of LAL was observed when the reactions were carried out at 0°C. (C) 2000 Academic Press.
KW - 4-hydroxy-TEMPO
KW - Chirality
KW - Free radical scavengers
KW - Free radicals
KW - Linoleyl alcohol
KW - Potato tuber lipoxygenase
KW - Stereoisomers
KW - cis,trans isomerism
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U2 - 10.1006/abbi.2000.1816
DO - 10.1006/abbi.2000.1816
M3 - Article
C2 - 10871046
AN - SCOPUS:0034213163
SN - 0003-9861
VL - 378
SP - 65
EP - 77
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -