中度嗜盐菌Martelella sp. AD-3 降解菲过程中水杨酸-5-羟化酶的酶学性质

目的]研究中度嗜盐菌Martelella sp.AD-3在降解菲过程中水杨酸-5-羟化酶的活性与菲降解效率的关系及其酶学性质.方法]通过HPLC分析菲的降解效率和AD-3菌粗酶液催化水杨酸的产物,根据NADH在340 nm处的吸光度变化计算水杨酸-5-羟化酶的活性.结果]水杨酸-5-羟化酶是一种诱导酶,在AD-3菌的对数生长期和稳定初期时活性较高,酶活力大小与该菌对菲的降解速率基本一致.在菲浓度为200 mg/L、生长盐度为3％、pH为9.0的培养条件下,AD-3菌株表达的水杨酸-5-羟化酶的活力最高,为132.8 nmol/(min·mg).水杨酸-5-羟化酶催化水杨酸降解时的最适温度、pH和盐度分别为30℃、7.5和3％,酶的最大反应速率为200 nmol/(min· mg)、米氏常数Km为8.7μmol/L.结论]AD-3菌在降解菲的过程中表达水杨酸-5-羟化酶,该酶的活性与菲降解速率具有相关性.

Characterization of salicylate 5-hydroxylase for phenanthrene degradation using moderately halophilic Martelella sp. AD-3

Objective] To identify the relationship between salicylate 5-hydroxylase activity and the degradation rate of phenanthrene by moderately halophilic Martelella sp.AD-3,and to investigate their enzymatic characteristics.Methods] The products resulted from degradation of salicylic acid using the crude enzyme produced by AD-3 was analyzed using HPLC analysis,and salicylate 5-hydroxylase activities at different conditions was calculated according to the change of NADH absorbance at 340 nm.Results] The salicylate 5-hydroxylase activity was higher during log-phase and early stationary phase of AD-3,and the enzyme activity was in consistent with phenanthrene degradation rate.The enzyme production was induced by phenanthrene and salicylic acid.The highest enzyme activity,132.8 nmol/(min·mg),from strain AD-3 was obtained under the phenanthrene concentration of 200 mg/L,3% salinity and a pH of 9.0.The optimum conditions for degradation of salicylic acid using this enzyme were 30℃,pH 7.5,and salinity 3%.The Vmax and Km for the enzyme were 200 nmol/(min·mg) and 8.7 μmol/L,respectively.Conclusion] The salicylate 5-hydroxylase was produced in the degradation of phenanthrene in AD-3.The enzyme activity was related to phenanthrene degradation rate.