Thank you very much for the reply. Actually, no water is observed to coordinate with the zinc ion in the complex structure of the enzyme and a substrate analog. The complex structure is determined at 2.3 Å resolution. Besides, in the complex structure, the zinc ion is already coordinated to six atoms thus forming an octahedral geometry.
Crystal 2012/7/23 Andrew Pannifer <a.panni...@beatson.gla.ac.uk> > Hi Crystal**** > > I reckon Roger Rowlett has the most likely explanation. The charge on the > Asp is delocalised over the carboxyl group and this tends to make it a > not-very-good nucleophile and combined with the Zn attracting some of this > charge, even less so. Deprotonated waters in contrast are good > nucleophiles and the more likely species to directly attack.**** > > Andrew**** > > ** ** > ------------------------------ > > *From:* CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] *On Behalf Of > *Crystal > Xu > *Sent:* 20 July 2012 06:32 > *To:* CCP4BB@JISCMAIL.AC.UK > *Subject:* [ccp4bb] Nucleophilic attack by the side-chain carboxyl group > of Asp?**** > > ** ** > > Hi everyone,**** > > I am studying the catalytic mechanism of an enzyme. My structural data > indicates that an Asp is of most possibility to sever as a general base. > The Asp residue is coordinated to a zinc ion. Would it be possible that > the side-chain carboxyl group of Asp attacks a carbon atom of the > substrate? Does anyone know any examples?**** > > Thanks very much.**** > > Best regards.**** > > ** ** >
