MBB 222 Lecture Notes - Lecture 14: Oxyanion Hole, Tetrahedral Carbonyl Addition Compound, Oxyanion
20 Dec 2018
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Document Summary
The carbonyl carbon of the acyl-enzyme intermediate is bonded to ser195 and has tetrahedral geometry!tetrahedral intermediate. A tetrahedral intermediate is a reaction intermediate in which the bond arrangement around an initially double-bonded (sp2) carbon atom, which is trigonal in geometry, is transformed to tetrahedral geometry. The tetrahedral intermediate results from nucleophilic addition to a carbonyl group. It is a short-lived intermediate in the reaction it is unstable in part due to the negative charge on the carbonyl oxygen (the oxyanion). It is the carbonyl carbon of the aromatic amino acid (r1) that is attacked by the alkoxide ion and forms the tetrahedral intermediate; the carbonyl oxygen is the oxyanion. The negatively charged oxyanion is temporarily stabilized by hydrogen- bonding with the backbone amide nitrogens of gly193 and ser195 this stabilization pocket formed by. Collapse of the tetrahedral intermediate, cleavage of the peptide bond and release of p1. The resulting acyl-enzyme intermediate is more stable than the tetrahedral intermediate.
