番茄植酸酶分离提纯及其特性研究

Purification and Characterization of Phytase Induced in Tomato Roots under PhosphorusDeficient Conditions

运用硫铵沉淀、阴离子交换柱层析、凝胶过滤、ＦＰＬＣ和活性电泳等技术，从缺磷条件下生长的番茄根抽提物中分离提纯了植酸酶．该酶是分子量约为８２ｋＤ的亚基组成的二聚体，等电点５．５，最适ｐＨ为４．３，对植酸钠具有很高亲和力（Ｋｍ＝３８μｍｏｌ／Ｌ）．番茄植酸酶活性受无机磷酸、钼和氟化物强烈抑制．氨基酸组成分析表明，该酶谷氨酸、天冬氨酸和甘氨酸含量较高．

Phytase is purified from roots of tomato plants grown under phosphorusdeficient conditions using five purification schemes. The phytase is successfully separated from the major acid phosphatase to an eletrophoretic homogeneity. The native molecular weight of this enzyme is estimated to be about 164 kD by BioGel P200 gel filtration. The molecular weight of the subunit on SDSPAGE is approximately 82 kD, indicating that the native form of the enzyme is a homodimer. The isoelectric point of tomato phytase is about 5.5. The enzyme exhibits a high affinity for phytic acid ( K m=38μmol/L), and is strongly inhibited by phosphtate, molybdate and fluoride. Among other characteristics of tomato phytase, the pH and temperature optima are 4.3 and 45℃, respectively. Tomato phytase contains a fairly high concentration of aspartic, glutamic acid and glycine residues.