Synthesis and inhibition studies of sulfur-substituted squalene oxide analogues as mechanism-based inhibitors of 2,3-oxidosqualene-lanosterol cyclase.
The synthesis and biological evaluation of three new sulfur-substituted oxidosqualene (OS) analogues (1-3) are presented. In these analogues, C-11, C-15, or C-18 in the OS skeleton was replaced by sulfur. The sulfur position in the OS skeleton was chosen to disrupt one or more key processes involved in cyclization: (a) the folding of the B-ring into a boat conformation, (b) the anti-Markovnikov cyclization leading to the C-ring, or (c) the formation of the D-ring during the lanosterol biosynthesis. Enzyme inhibition kinetics using homogeneous mammalian oxidosqualene cyclases (OSC) were also examined for the previously reported S-19 analogue 4. The four analogues were potent inhibitors of mammalian OSCs (IC50 = 0.05-2.3 microM for pig and rat liver OSC) and fungal cell-free Candida albicans OSC (submicromolar IC50 values). In particular, the S-18 analogue 3 showed the most potent inhibition toward the rat liver enzyme (IC50 = 50 nM) and showed potent, selective inhibition against the fungal enzyme (IC50 = 0.22 nM, 10-fold more potent than the S-19 analogue 4). Thus, 3 is the most potent OSC inhibitor known to date. The Ki values ranged from 0.5 to 4.5 microM for pig OSC, with 3 and 4 showing about 10-fold higher potency for rat liver OSC. Interestingly, the S-18 analogue 3 showed time-dependent irreversible inhibition with homogeneous pig liver OSC (kinact = 0.06 min-1) but not with rat OSC.
Stach
D
D
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
Zheng
Y F
YF
Perez
A L
AL
Oehlschlager
A C
AC
Abe
I
I
Prestwich
G D
GD
Hartman
P G
PG
D000818:Animals; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology*; D019751:Intramolecular Transferases; D007535:Isomerases / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008968:Molecular Conformation; D051381:Rats; D013185:Squalene / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D013455:Sulfur / Q000737:chemistry*; D013552:Swine
C002821:2,3-oxidosqualene; D004791:Enzyme Inhibitors; D013455:Sulfur; D013185:Squalene; D007535:Isomerases; D019751:Intramolecular Transferases; C021924:lanosterol synthase