English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Homology models of the active site of cytochrome P450 2D6 (CYP2D6) have identified phenylalanine 481 (Phe(481)) as a putative ligand-binding residue, its aromatic side chain being potentially capable of participating in pi-pi interactions with the benzene ring of ligands. We have tested this hypothesis by replacing Phe(481) with tyrosine (Phe(481)--&gt;Tyr), a conservative substitution, and with leucine (Phe(481)--&gt;Leu) or glycine (Phe(481)--&gt;Gly), two non-aromatic residues, and have compared the properties of the wild-type and mutant enzymes in microsomes prepared from yeast cells expressing the appropriate cDNA-derived protein. The Phe(481)--&gt;Tyr substitution did not alter the kinetics [K(m) (microM) and V(max) (pmol/min per pmol) respectively] of oxidation of S-metoprolol (27; 4.60), debrisoquine (46; 2.46) or dextromethorphan (2; 8.43) relative to the respective wild-type values [S-metoprolol (26; 3.48), debrisoquine (51; 3.20) and dextromethorphan (2; 8.16)]. The binding capacities [K(s) (microM)] of a range of CYP2D6 ligands to the Phe(481)--&gt;Tyr enzyme (S-metoprolol, 22.8; debrisoquine, 12.5; dextromethorphan, 2.3; quinidine, 0.13) were also similar to those for the wild-type enzyme (S-metoprolol, 10.9; debrisoquine, 8.9; dextromethorphan, 3.1; quinidine, 0.10). In contrast, the Phe(481)--&gt;Leu and Phe(481)--&gt;Gly substitutions increased significantly (3-16-fold) the K(m) values of oxidation of the three substrates [S-metoprolol (120-124 microM), debrisoquine (152-184 microM) and dextromethorphan (20-31 microM)]. Similarly, the K(s) values of the ligands to Phe(481)--&gt;Leu and Phe(481)--&gt;Gly mutants were also increased 3 to 10-fold (S-metoprolol, 33.2-41.9 microM; debrisoquine, 85-90 microM; dextromethorphan, 15.7-18.8 microM; quinidine 0.35-0.53 microM). However, contrary to a recent proposal that Phe(481) has the dominant role in the binding of substrates that undergo CYP2D6-mediated N-dealkylation routes of metabolism, the Phe(481)--&gt;Gly substitution did not substantially decrease the capacity of the enzyme to N-deisopropylate metoprolol (wild-type, 1.12 pmol/min per pmol of P450; Phe(481)--&gt;Gly, 0.71), whereas an Asp(301)--&gt;Gly substitution decreased the N-dealkylation reaction by 95% of the wild-type rate. Overall, our results are consistent with the proposal that Phe(481) is a ligand-binding residue in the active site of CYP2D6 and that the residue interacts with ligands via a pi-pi interaction between its phenyl ring and the aromatic moiety of the ligand. However, the relative importance of Phe(481) in binding is ligand-dependent; furthermore, its importance is secondary to that of Asp(301). Finally, contrary to predictions of a recent homology model, Phe(481) does not seem to have a primary role in CYP2D6-mediated N-dealkylation.

Influence of phenylalanine-481 substitutions on the catalytic activity of cytochrome P450 2D6