蛋白水解酶催化机制的研究

Study on Catalytic Mechanism of Proteolytic Enzymes

用CNDO/2计算了模拟蛋白水解酶的不同底物中,酰胺键和酯键的电子参数及水解反应的中间四面体产物的电子特性,表明取代基的特性和羰基形成的氢键不影响酰胺基的电荷和键序.讨论了酰胺的电子状态与它的平面结构的曲变程度密切相关.指出在双环β-内酰胺中缺乏共振稳定性.在酰胺中,计算了不同杂化状态时,酰胺氮原子的不同pKa值.

Electronic parameters of amid and ester in some compounds modelling substrates of proteolytic enzymes, and electronic properties of corresponding tetrahedral compounds, which are intermediates of the hydrolytic reaction, are calculated by the CNDO/2 method. The nature of substituents and the formation of the hydrogen bond by the carbonyl oxygen atom are shown to have no suffcient influence on the charge and bond orders of the amide group. The dramatic dependence of the amide electronic state from the distort degree of its planar structure is found. The resonance stabilization is shown to be absent in the bicyclic β - lactams. The pKa values of the amide nitrogen atom are calculated at various hybridization states in amides.