Partitioning of Catechol Derivatives in Lipid Membranes: Implications for Substrate Specificity to Catechol-O-methyltransferase

Publication year: 2020
Authors: Parkkila P., Viitala T.

Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, 00014 Helsinki, Finland

Published in: ACS Chemical Neuroscience, 2020, Vol.11, 6, p. 969–978
doi: 10.1021/acschemneuro.0c00049

We have utilized multiparametric surface plasmon resonance and impendance-based quartz crystal microbalance instruments to study the distribution coefficients of catechol derivatives in cell model membranes. Our findings verify that the octanol–water partitioning coefficient is a poor descriptor of the total lipid affinity for small molecules which show limited lipophilicity in the octanol–water system. Notably, 3-methoxytyramine, the methylated derivative of the neurotransmitter dopamine, showed substantial affinity to the lipids despite its nonlipophilic nature predicted by octanol–water partitioning. The average ratio of distribution coefficients between 3-methoxytyramine and dopamine was 8.0. We also found that the interactions between the catechols and the membranes modeling the cell membrane outer leaflet are very weak, suggesting a mechanism other than the membrane-mediated mechanism of action for the neurotransmitters at the postsynaptic site. The average distribution coefficient for these membranes was one-third of the average value for pure phosphatidylcholine membranes, calculated using all compounds. In the context of our previous work, we further theorize that membrane-bound enzymes can utilize membrane headgroup partitioning to find their substrates. This could explain the differences in enzyme affinity between soluble and membrane-bound isoforms of catechol-O-methyltransferase, an essential enzyme in catechol metabolism.

MP-SPR keywords: drug interaction on lipids, model membrane, small molecular weight drugs