丝素蛋白具有良好的反应性,利用酪氨酸酶对丝素中酪氨酸残基的催化氧化特性,进行了酶促荧光素在丝素蛋白表面接枝研究,探讨了丝素材料酶促改性的反应机制.在分析酪氨酸酶动力学性质基础上,借助于紫外光度法、荧光光谱法和体积排阻色谱等对5-氨基荧光素在丝素表面的接枝效果进行了分析.研究结果表明,以 L-dopa 为底物时,酪氨酸酶的Vmax＝11．98 U/min,Km＝2．15 mmol/L,增加反应体系氧浓度有利于酶促反应；酶促丝素改性中,酪氨酸酶不但会催化丝素蛋白和氨基荧光素发生接枝反应,也会使丝素蛋白大分子间发生自交联.
Silk fibroin has satisfactory reactivity and tyrosinase has the potential ability to catalyze the oxidation of the tyrosine residues in silk fibroins.The paper investigated the efficacy of the enzymatic grafting of fluores-cein onto silk fibroin,aiming at realizing the mechanism of enzymatic modification of silk materials.The kinet-ics of the enzymatic reaction with tyrosinase were evaluated,and the efficacies of the enzymatic grafting of 5-aminofluorescein onto silk fibroins were also measured in terms of UV spectrophotometry,fluorescence spectra and size exclusion chromatography.The results showed that when L-dopa was used as substrate,the Vmax and Km of tyrosinase reached to 11.98 U/min and 2.15 mmol/L,respectively.Higher concentration of oxygen could promote the enzymatic oxidation.During the enzymatic modification of silk fibroin,tyrosinase not only catalytic the grafting reaction between silk fibroin and aminofluorescein,but also cause self-crosslinking among silk fi-broin molecules.
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