果菠萝蛋白酶在有机溶剂微扰时的分子折叠与活力变化的研究

本文用荧光、紫外差示及CD光谱研究果菠萝蛋白酶经甲醇、乙醇、乙二醇微扰后的构象与活力变化情况.酶的荧光强度随有机溶剂浓度增大而增强,表明Tyr、Trp微环境发生明显变化。232nm和285nm处出现紫外差吸收正峰。前峰与酶分于折叠的变化有关,而后峰与Tyr、Trp微环境的变化相关.甲醇、乙醇微扰后,天然酶的208nm和225nmCD双负峰逐渐加强,而乙二醇微扰后,225nm负峰加强。208nm负峰减弱并红移直至完全消失,说明酶分子完全伸展.

Effect of Organic Solvents on the Molecular Folding and the Enzyme Activity of Fruit Bromelain

Changes of the molecular folding of fruit bromelain perturbed by methanol, ethanol and ethylene glycol have been studied by means of measuring the fluorescence spectra, differential UV-ab-sorbed spectra and circular dichroism spectra. The fluorescence intensity of the enzyme increased distinctly with increasing organic solvent concentrations, suggesting that the microenvironments of aromatic amino acids have distinctly changed. The differential UV-absorbed spectra showed that there were two positive peaks at 232 nm and 288 nm, both of them intensified with increasing concentrations of organic solvents. The 232 nm peak is in concordance with the change of the folding of the enzyme molecules, while the 285 nm peak is in concordance with the change of the microenvironments of tyrosine and tryptophan residues. The circular dichroism spectra showed that the natural enzyme has two negative peaks at 208 nm and 225 nm. These negative peaks of the enzyme perturbed by methanol and ethanol intensified obviously, but in the presence of ethylene glycol, the 225 nm peak increased, while the 208 nm peak decreased and red-shifted in position, eventually the peak disappeared completely at a concentration of 50% of ethylene glycol, indicating that the enzyme molecule has extended completely.