to determine the origin of the overall approximately 10 ( 16 ) -fold rate enhancement of dna hydrolysis catalyzed by staphylococcal nuclease , the effects of single mutations that alter the amino acid residue at each of the essential positions asp-21 , asp-40 , thr-41 , arg-35 , and arg-87 have been examined .
C0002525
amino acid
C0040005
thr