以H3 PW12 O40和H4 SiW12 O40(简写为PW12和SiW12)为效应物,测定其对酪氨酸酶活力的抑制作用.通过非变性聚丙烯凝胶( Native-PAGE)电泳确定酪氨酸酶是多家族基因编码,其分子量为3×104~3.4×104,4.2×104~4.6×104,6.4×104~6.8×104,且均具有活性,测定PW12和SiW12对酪氨酸酶的抑制效果,并结合酶动力学法研究其抑制机理.结果表明,当PW12和SiW12浓度分别达到13和25 mmol/L时,酪氨酸酶的活力完全被抑制,即PW12和SiW12对酪氨酸酶二酚酶具有不同程度的抑制效果.当所加酶量为0.0173 mg/mL时, PW12和SiW12对酪氨酸酶二酚酶活力的半抑制率( IC50)分别为1.57和2.31 mmol/L,它们对酪氨酸酶二酚酶的抑制均为可逆过程.其中, PW12对二酚酶的抑制类型为混合型,其KI及KIS分别为0.34和0.43 mmol/L, SiW12对二酚酶的抑制类型表现为竞争型,其KI为0.59 mmol/L.综合考虑IC50值和抑制常数等参数, PW12对酪氨酸酶二酚酶的抑制能力优于SiW12.%H3 PW12 O40 and H4 SiW12 O40 ( abbreviated as PW12 and SiW12 ) were taken as inhibitors and their inhibitory effects and mechanisms on mushroom tyrosinase were evaluated by Native polyacrylamide gel electro-phoresis( PAGE) electrophoresis method and kinetic enzymatic method. The Native-PAGE electrophoresis re-sults show that tyrosinase are encoded by a multigene family, their molecular weight are mainly 3í104-3.4í104 , 4.2í104-4.6í104 and 6.4í104-6.8í104 , which were all active. The inhibitory effects of Kiggin-type polyoxotungstates, H3 PW12 O40 and H4 SiW12 O40 on mushroom tyrosinase were evaluated, and then the inhibito-ry mechanisms were further studied combined with the kinetic enzymatic method. The results indicated that the enzyme was inactive when the concentration of PW12 and SiW12 was 13 and 25 mmol/L, respectively. More-over, the kinetic enzymatic method suggested that both PW12 and SiW12 exhibited potent inhibitory activities with IC50 value of 1.57 and 2.31 mmol/L, respectively. PW12 was found to be a mixed-type inhibitor with KI=0.34 mmol/L and KIS=0.43 mmol/L, while SiW12 was suggested to be competitive inhibitor of tyrosinase with KI of 0.59 mmol/L. Based on a comprehensive consideration of IC50 and inhibitory constants, PW12 was more effective against mushroom tyrosinase than SiW12 .
展开▼
