Proton-Dissociation Behavior of Sulfonium-Salt Pendants Having a Coumarin Skeleton Introduced into the α-Chymotrypsin Active Site

Masami ISHIHARA, Kanji KUBO†, Hiroyuki WATANABE and Tadamitsu SAKURAI*

Department of Applied Chemistry, Faculty of Engineering, Kanagawa University; Kanagawa-ku, Yokohama-shi 221-8686 Japan
† Institute of Advanced Material Study, Kyushu University; Kasuga-koen, Kasuga-shi 816-0811 Japan

Spectroscopic behavior of the coumarinyl-substituted sulfonium-salt pendants attached to the methionine-192 residue of α-chymotrypsin was compared with that of the corresponding reference sulfonium saltsDIt was suggested that a spatial arrangement of the coumarin ring and a water molecule immobilized in this enzyme binding site play critical roles in determining the acidity of the pendants in the ground and excited singlet states, respectively.


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