钒取代型多金属氧酸盐对酪氨酸酶的抑制作用

测定了自制的α-1,2,3-K6H[SiW9V3O40]、α-1,2-K6[SiW10V2O40]和α-K5[SiW11VO40](以下分别简写为α-SiW9V3、α-SiW10V2和α-SiW11V)钒取代多金属氧酸盐对蘑菇酪氨酸酶活性的抑制作用。 结果表明，在pH=6.8的NaH2PO4-Na2HPO4缓冲溶液中，α-SiW9V3对酪氨酸酶有较强的抑制作用，表现为对酶稳态活力的抑制作用和对迟滞时间的延长作用，在DMSO溶液中，其IC50为0.6841 mmol/L，0.7 mmol/L α-SiW9V3可使单酚酶的迟滞时间由235 s延长至650 s，增加了2.77倍。 α-SiW9V3对酪氨酸酶单酚酶的抑制为可逆作用过程，抑制类型为混合型，其抑制常数KI、KIS分别为4.22和2.39 mmol/L。 α-SiW10V2不溶于DMSO，故未研究其对酶的抑制作用，α-SiW11V对酪氨酸酶抑制作用很弱。

Inhibition Effect of Vanadate-replaced Polyoxometalates on Mushroom Tyrosinase

Three kinds vanadate-replaced polyoxometalates, α-1,2,3-K6H[SiW9V3O40], α-1,2-K6[SiW10V2O40] and α-K5[SiW11VO40](abbreviated as α-SiW9V3, α-SiW10V2, α-SiW11V) were synthesized and evaluated as tyrosinase inhibitors using the enzymological kinetic method. The results demonstrate that α-SiW9V3 can inhibit tyrosinase strongly, as demonstrated by the inhibition of the steady-state activity of the enzyme and the lengthening of the lag time. The IC50 of α-SiW9V3 was estimated to be 0.6841 mmol/L for the inhibition of mushroom tyrosinase. It resulted in the lag time of the monophenolase extension from 235 s to 650 s with 0.7 mmol/L of α-SiW9V3. The inhibition of α-SiW9V3 on monophenolase of mushroom tyrosinase proceeds as reversible process, and the inhibition of α-SiW9V3 is a competitive-uncompetitive mixed-Ⅱ type due to the oxidation of L-tyrosine. The inhibition constants(KI and KIS) are determined to be 4.22 mmol/L and 2.39 mmol/L, respectively. As for the α-SiW10V2, however, it is unsoluble in DMSO buffer, and its effect on the mushroom tyrosinase cannot be studied. While the inhibition ability of α-SiW11V on tyrosinase activity is rather weak.