Catalytic mechanism of scytalone dehydratase from Magnaporthe grisea

✍ Scribed by Jordan, Douglas B; Basarab, Gregory S; Steffens, James J; Lundqvist, Tomas; Pfrogner, Beverly R; Schwartz, Rand S; Wawrzak, Zdzislaw

• Book ID: 101215281
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 109 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199903)55:3<277::aid-ps893>3.0.co;2-1

✦ Synopsis

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-4Hbenzopyran-4-one (DDBO), was nearly equal to scytalone as substrate for the enzyme, and DDBO's anomeric eþ ect 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 enzymecatalyzed dehydration reactions. A concerted E2 elimination for the catalytic mechanism is proposed.