Abstract:

As a biodegradable macromolecule，chitosan functions with unique characteristics. However，limited by its solubility and other factors，chemical method is used to improve chitosan’s properties. As chemical modifications can cause environmental pollution，need more reactive steps and suffer from poor specificity，biological modification methods get more attention. As a dual-function biological catalyst，tyrosinase catalyzes two different oxygen-dependent reactions that occur consecutively，o-hydroxylation of monophenols to yield o-diphenols（cresolase activity）and the subsequent oxidation of o-diphenols to o-quinones（catecholase activity）. Tyrosinase specificly grafts phenolic compounds to chitosan to improve its solubility. Tyrosinase oxides o-diphenols of o-quinone and plays the role of cross-linking agent to reinforce the tensile properties of chitosan membrane. Tyrosinase oxides protein tyrosine residues to form chitosan conjugates. With further research，tyrosinase’s application on chitosan biological modification will be more extensive.

摘要：

作为生物可降解性大分子，壳聚糖具有独特的功能特性，但是受其溶解性等因素的限制，以往常采用化学法进行改性以期改善其相关性质，由于化学改性带来的环境污染、反应步骤多、专一性差等问题，生物法改性日益得到人们的关注。酪氨酸酶作为一种双重功能的生物催化剂，可连续地催化与氧有关的二个不同的反应，即单酚经邻羟基化为邻酚（苯甲酚酶活性）和随后邻酚氧化为邻醌（邻苯二酚酶活性）。酪氨酸酶可将特定的酚类化合物接枝到壳聚糖上，改善了壳聚糖的溶解性；酪氨酸酶将二酚氧化为邻醌，起到交联剂的作用而增强壳聚糖膜的抗张性能；酪氨酸酶可将蛋白质的酪氨酸残基氧化，从而与壳聚糖结合生成缀合物。随着研究的进一步深入，酪氨酸酶在壳聚糖生物改性的应用将更加广阔。