无花果蛋白酶在胍溶液中的分子折叠与活力变化研究

Studies on the Relationship Between the Molecular Folding and Activity of Ficin Guanidine Hydrochloride

本文研究无花果蛋白酶（ＥＣ．３．４．４．１２）在不同浓度盐酸胍溶液中分子构象与活力变化关系。酶的内源荧光光谱，圆二色光谱与酶活力的变化表明：荧光光谱呈现二个明显的变化区域，低浓度胍（低于２ｍｏｌ／Ｌ）中，荧光发射峰基本不变，但荧光强度随胍浓度上升，随胍浓度断续增大（高于２ｍｏｌ／Ｌ），酶的最大发射波长明显红移。当胍浓度低于１ｍｏｌ／Ｌ时，不仅不会使酶失活，反而使酶激活，当胍浓度高于１ｍｏｌ／Ｌ以上时，酶逐渐失活，使酶完全失活的胍浓度为６ｍｏｌ／Ｌ酶的圆二色光谱也随着胍浓度的改变而发生复杂的变化。将荧光变化，ＣＤ谱变化及活力改变结合起来，表明活力的激活与构象的明显变化似是同步发生的，从另一角度进一步说明酶活性部位柔性是充分表现酶活力所必需。

Changes of activity and conformation of ficin (EC 3,4,4,12) in different concentrations of guanidine solution have been studied. Two distinct areas were found in fluorescence spectra:the wavelength of the emission peaks remained unchanged below 2 mol/L GuHCl, but the fluorescence intensity increased with increasing GuHCl concentration. When the concentrations of GuHCl were greater than 2 mol/L, the emission peaks began to redshift.A fascinating phenomenon was found with the changes in activity. Instead of showing a decrease in activity, the enzyme was found to be activated when GuHCl concentrations were below 1 mol/L, when GuHCl concentration were greater than 1 mol/L,the enzyme activities began to decrease and was totally lost at 6 mol/L GuHCl. The CD spectra also gave a complex result. The relationship between activity and conformational change of ficin seemed to be basically synchronous. It also shows that an appropriate flexibility at the active site is essential for the full expression of enzyme activity.