catalytic mechanism of scytalone dehydratase from <toggle>magnaporthe grisea</toggle><fnr href="fn1"></fnr><fn id="fn1">based on poster presentations at the 9th international congress of pesticide chemistry, organised by the international union of pure and applied chemistry (iupac), and held in london, uk, 2–7 august 1998.</fn>

The catalytic mechanism of scytalone dehydratase was examined by studying alternative substrates and site-directed mutations of active-site residues. Searches for an enol intermediate by looking for a half-reaction with authentic scytalone and 3,4-dihydro-6,8-dihydroxy-1-(2H)-2-[¹³C]naphthalenone were negative. An alternative substrate, 2,3-dihydro-2,5-dihydroxy-4H-benzopyran-4-one (DDBO), was nearly equal to scytalone as substrate for the enzyme, and DDBO's anomeric effect in stabilizing a partial carbocation center at C3 does not substantially contribute to the mechanism. Kinetic analysis of site-directed mutations of active-site amino acid side chains within the enzyme's active site provided an account for the role of these residues in the enzyme-catalyzed dehydration reactions. A concerted E2 elimination for the catalytic mechanism is proposed. © 1999 Society of Chemical Industry