The elect
ronic
and ste
ric const
raints of the dopamine
rs/beta2.gif" BORDER=0 ALIGN="middle">-monooxygenase (D
rs/beta2.gif" BORDER=0 ALIGN="middle">M; E.C.1.14.17.1)active site we
re studied using a se
ries of chi
ral bisubst
rateinhibito
rs. The (R)
and (S) enantiome
rs of5-phenyl-2-thiooxazolidone we
re appa
rent bisubst
rate inhibito
rs fo
rD
rs/beta2.gif" BORDER=0 ALIGN="middle">M with
respect to ty
ramine
anddioxygen, but with small enantiome
ric selectivity. In cont
rast tothe subst
rate specificity of the enzyme,N-methylation of both inhibito
rs inc
reased the potency without alte
ringthe enantiome
ric selectivity. The(S) C-4-methyl substitution was mo
re det
rimental towa
rd the inhibitionpotency compa
red to (R) C-4-methyl substitution fo
r both the (R)
and (S) se
ries, which was alsoopposite of the subst
rate specificity ofthe enzyme. The high inhibition potency
and appa
rent bisubst
ratebehavio
r of 3-phenyl-1,5-bisthiogluta
rimide (
XVI), a p
robe designed to mimic two distinctbinding modes fo
r the (R)
and (S) inhibito
rs,suggested that they may inte
ract with the enzyme by two diffe
rent modesinvolving both coppe
rs in theactive site. Di
rect suppo
rt fo
r the inte
raction of the thioneg
roup(s) of
XVI with the
reduced D
rs/beta2.gif" BORDER=0 ALIGN="middle">Mcoppe
r(s)is p
rovided by the UV-vis spect
roscopic studies. The completedisappea
rance of the cha
racte
ristic UVabso
rption of
XVI at 336 nm in the p
resence ofstoichiomet
ric amounts of
reduced D
rs/beta2.gif" BORDER=0 ALIGN="middle">M demonst
ratethat it could be an active site tit
rant fo
r reduced D
rs/beta2.gif" BORDER=0 ALIGN="middle">M. Theability of the enzyme to inte
ract with theseinhibito
rs by mo
re than one mode suggests that the D
rs/beta2.gif" BORDER=0 ALIGN="middle">M active sitepossesses high ste
ric
and elect
ronictole
rance.