Avaeva S, Ignatov P, Kurilova S, Nazarova T, Rodina E, Vorobyeva N, Oganessyan V, Harutyunyan E
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russian Federation.
FEBS Lett. 1996 Dec 9;399(1-2):99-102. doi: 10.1016/s0014-5793(96)01296-3.
Aspartic acids 65, 67, 70, 97 and 102 in the inorganic pyrophosphatase of Escherichia coli, identified as evolutionarily conserved residues of the active site, have been replaced by asparagine. Each mutation was found to decrease the k(app) value by approx. 2-3 orders of magnitude. At the same time, the Km values changed only slightly. Only minor changes take place in the pK values of the residues essential for both substrate binding and catalysis. All mutant variants have practically the same affinity to Mg2+ as the wild-type pyrophosphatase.
已将大肠杆菌无机焦磷酸酶中被鉴定为活性位点进化保守残基的天冬氨酸65、67、70、97和102替换为天冬酰胺。发现每个突变都会使表观一级反应速率常数（k(app)）值降低约2至3个数量级。同时，米氏常数（Km）值仅略有变化。对于底物结合和催化均至关重要的残基的解离常数（pK）值仅发生微小变化。所有突变变体对Mg2+的亲和力与野生型焦磷酸酶几乎相同。
