香樟酪氨酸酶对NAA诱导的响应及其生化性质研究

Response of Tyrosinase in Cinnamomum camphora to NAA Induction and Its Biochemical Characteristics

以离体香樟叶片和果实为材料,研究了萘乙酸（NAA）处理对其中酪氨酸酶及其同工酶活性的影响,并对香樟果实中酪氨酸酶进行分离纯化,初步分析了该酶基本生化特征.结果表明：（1）10μmol·L^-1NAA处理对香樟叶片同工酶TYRL2有较强的激活作用,对同工酶TYRL1有抑制作用,1.0和0.1μmol·L^-1浓度的NAA对同工酶TYRL3有激活作用;（2）在香樟果实的酪氨酸酶同工酶中,TYRF1的活性最高并在果实成熟过程中逐渐增强,100μmol·L^-1的NAA对果实成熟以及酪氨酸酶的酶活性都有一定的促进作用;（3）经纯化的香樟果实酪氨酸酶最适pH值为7.5,最适温度为50℃,亚基分子量为43KDa;以L-DOPA为底物时的Km为12.82mmol·L^-1,Vmax为80.65U·mg^-1蛋白;其在酸性（pH4-7）和高温（40-70℃）条件下较稳定.可见,不同浓度的NAA对香樟叶片和果实中的酪氨酸酶活性有不同程度的激活和抑制作用.

Effect of treatment with different NAA concentrations on the tyrosinase （TYR） and its isozyme activities in leaf and fruit of Cinnamomum camphora was investigated. 10 μmol · L^-1 NAA increased the activity of TYR 1.2 in leaf and inhibited TYR L1,1 μmol · L^-1 ,0.1 μmol · L^-1NAA increased the activity of TYR L3 also; High concentration of NAA （100 μmol · L^-1） stimulated not only the maturity of the fruit, but also increased the activity of TYR in fruit. A TYR was purified by the processes.tissue homogenation, ammonium sulfate, Sephadex G-100 and DEAE-Sepharose. The optimum pH and temperature of the purified TYR was 7.5 and 50℃ respectively. The molecular weight of its subunit was 43 kDa. Its apparent Km of L-DOPA was 12.82 mmol· L^-1 ,the Vmax was 80. 65 U·mg^-1 protein. The result revealed that different concentrations of NAA had the different effect on activity of TYR in both leaf and fruit.