Lipoxygenase inhibitory activity of alkyl protocatechuates.
Alkyl 3,4-dihydroxybenzoates (protocatechuates) inhibited linoleic acid peroxidation catalyzed by soybean lipoxygenase-1 (EC 1.13.11.12, Type 1). Their inhibitory activities displayed a parabolic function of their lipophilicity and maximized with alkyl chain lengths of between C11 and C14. Tetradecanyl protocatechuate exhibited the most potent inhibition with an IC50 of 0.05 μM, followed by dodecyl (lauryl) protocatechuate with an IC50 of 0.06 μM. However, their parent compound, protocatechuic acid, did not show this inhibitory activity up to 200 μM, indicating that the alkyl chain length is significantly related to the inhibition activity. The allosteric (or cooperative) inhibition of soybean lipoxygenase-1 of longer alkyl protocatechuates is reversible but in combination with their iron binding ability to disrupt the active site competitively and to interact with the hydrophobic portion surrounding near the active site (sequential action). In the case of dodecyl protocatechuate, the enzyme quickly binds this protocatechuate and then its dodecyl group undergoes a slow interaction with the hydrophobic domain in close proximity to the active site in the enzyme. The inhibition kinetics analyzed by Lineweaver-Burk plots indicates that octyl protocatechuate is a competitive inhibitor and the inhibition constant (Ki) was obtained as 0.23 μM but dodecyl protocatechuate is a slow binding inhibitor.
Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, United States.
Tae Joung
TJ
Ha
Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, United States.
Kuniyoshi
K
Shimizu
Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3114, United States. Electronic address: ikubo@berkeley.edu.
Isao
I
Kubo
D001667:Binding, Competitive; D020134:Catalytic Domain; D002614:Chelating Agents / Q000737:chemistry; D005504:Food Analysis / Q000379:methods*; D057927:Hydrophobic and Hydrophilic Interactions; D020128:Inhibitory Concentration 50; D007501:Iron / Q000737:chemistry; D019787:Linoleic Acid / Q000737:chemistry*; D008084:Lipoxygenase / Q000737:chemistry*; D016859:Lipoxygenase Inhibitors / Q000737:chemistry*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry; D017434:Protein Structure, Tertiary; D013025:Glycine max / Q000201:enzymology; D013501:Surface-Active Agents
D002614:Chelating Agents; D016859:Lipoxygenase Inhibitors; D013501:Surface-Active Agents; D019787:Linoleic Acid; D007501:Iron; D010544:Peroxidases; C101084:lipoxygenase L-1; D008084:Lipoxygenase
Alkyl protocatechuates; Competitive inhibitor; Lipoxygenase inhibitors; Slow-binding inhibitor