Stern M S, Doscher M S
FEBS Lett. 1984 Jun 11;171(2):253-6. doi: 10.1016/0014-5793(84)80498-6.
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.
牛胰核糖核酸酶1 - 118位残基与包含该酶111 - 124位残基的合成十四肽通过非共价相互作用形成的完全活性半合成酶，使得对天冬氨酸-121在分子功能中的作用进行直接测试成为可能。用天冬酰胺取代该残基会产生一种衍生物，在标准测定条件下，于pH 7.0时对胞苷2',3'-环磷酸酯的活性为4.5%。在pH 5.8时对相同底物的进一步研究表明，活性降低完全是由于催化效率降低，而非对底物的亲和力下降。
