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Aspartic acid‐121 functions at the active site of bovine pancreatic ribonuclease
Author(s) -
Stern Mary S.,
Doscher Marilynn S.
Publication year - 1984
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(84)80498-6
Subject(s) - bovine pancreatic ribonuclease , active site , chemistry , aspartic acid , ribonuclease , residue (chemistry) , pancreatic ribonuclease , asparagine , substrate (aquarium) , enzyme , covalent bond , biochemistry , stereochemistry , cytidine , amino acid , organic chemistry , biology , rna , ecology , gene
The fully active semisynthetic enzyme formed by the non‐covalent interaction of residues 1–118 of bovine pancreatic ribonuclease and a synthetic tetradecapeptide containing residues 111–124 of the enzyme has allowed a direct test of the role of aspartic acid‐121 in the functioning of the molecule. Replacement of this residue by asparagine results in a derivative that is 4.5% active against cytidine 2',3'‐cyclic phosphate at pH 7.0 under standard assay conditions. Further studies with the same substrate at pH 5.8 reveal that the reduced activity results entirely from a diminished catalytic efficiency and not from a decreased affinity for substrate.