Unfortunately, their isn't a "general rule" for good versus bad nucleophiles. However, their are some key classical examples, which are reviewed extensively in enzymology textbooks. Remember, that a nucleophile is dependent on it's pKa value, which depends on the surrounding residues. Thus, two different enzymes that possess the same type of nucleophile but perform different reactions can have different pKa values, and therefore different rates. It is also dependent on the leaving group potential of the electrophile and the stability of the covalent intermediate. Some examples of nucleophiles in no particular order include, serine, cysteine, aspartate, lysine, histidine, and tyrosine. Hope this help.
Justin On 7/21/12 1:03 AM, "Peter Hsu" <hsuu...@u.washington.edu> wrote: >I too am also studying the reaction mechanism of an enzyme, but my >chemistry/enzymatic biochemistry is rather weak after many years of >non-use and no review. Does anyone know just as a general rule which >residues are the best to worst nucleophiles? > >Sorry if this seems rather presumptuous, just not sure where to look in >literature for a summary of these things.