4-coumarinyl ring with Phe221 and His480. This molecular
arrangement induced p–p stacking of phenylsulfonyl, triazole
and 4-coumarinyl rings with Phe221; and hydrogen bonding of triazole
(N3 position) with Ser478, and oxycoumarinyl moiety with
Arg192. Such interactions involve molecules in the bent form
(35), which arises from m-substitution of the sulfonyl group and
triazole ring on the phenyl ring of sulfonamide. The results suggested
that the Ser478 and Arg192 residues were essential for
the inhibition of aromatase. It should be noted that both Ser478
and Arg192 played crucial roles in anti-aromatase activity of the
natural substrate ASD.9 Accordingly, such amino acids participated
in a water-mediated network of hydrogen bonding, thereby allowing
the interaction between the aromatase and the C3-keto oxygen
of androstenedione to undergo enolization.9 Furthermore, Ser478
was capable of promoting the aromatase inhibition confirmed by
the mutagenesis study.12 In addition, such amino acid was the
residue responsible for the inhibition and selectivity.13,1