Substrate-based inhibitors of lanosterol 14 alpha-methyl demethylase: II. Time-dependent enzyme inactivation by selected oxylanosterol analogs.
Selected 15-, 32-, and 15,32-substituted lanosterol analogs are shown here to display time-dependent inactivation and lanosterol 14 alpha-methyl demethylase. These molecules are competitive with respect to substrate and require NADPH and O2 in order to display time dependence, thus supporting the premise that they are mechanism-based inactivators. Structural features required for lanosterol demethylation by the lanosterol demethylase such as nuclear double bond location and availability of an abstractable 15 alpha-proton are also essential elements for time-dependent inactivation. 32-(S)-Vinyllanost-8-en-3 beta,32-diol is a potent time-dependent inactivator (Kinact/Ki = 0.36 min-1 microM-1), while the 32-(R)-vinyllanost-8-en-3 beta,32-diol functions solely as a competitive demethylase inhibitor. These results support the premise that stereoselective oxidation occurs during lanosterol demethylation and that the 32-pro-S proton is abstracted during the demethylation reaction.
Trzaskos
J M
JM
Du Pont Merck Pharmaceutical Company, Wilmington, Delaware 19880-0400, USA.
Fischer
R T
RT
Ko
S S
SS
Magolda
R L
RL
Stam
S
S
Johnson
P
P
Gaylor
J L
JL
D001667:Binding, Competitive; D065607:Cytochrome P-450 Enzyme Inhibitors; D007700:Kinetics; D007810:Lanosterol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D010100:Oxygen / Q000494:pharmacology; D013237:Stereoisomerism; D058886:Sterol 14-Demethylase; D013329:Structure-Activity Relationship
C094921:32-vinyllanost-8-en-3,32-diol; D065607:Cytochrome P-450 Enzyme Inhibitors; D007810:Lanosterol; D009249:NADP; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D010100:Oxygen