在25℃,pH=6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究了香草醛对酪氨酸酶单酚酶和二酚酶活性的抑制效应.实验结果表明:香草醛对酪氨酸酶单酚酶和二酚酶活性均有抑制作用,其半数抑制浓度(IC50)约分别为2.7和4.1mmol/L;香草...在25℃,pH=6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究了香草醛对酪氨酸酶单酚酶和二酚酶活性的抑制效应.实验结果表明:香草醛对酪氨酸酶单酚酶和二酚酶活性均有抑制作用,其半数抑制浓度(IC50)约分别为2.7和4.1mmol/L;香草醛能明显延长单酚酶的迟滞时间,4 mmol/L香草醛能使迟滞时间由1.1 m in延长至3m in;Lineweaver-Burk图显示香草醛对二酚酶的抑制作用表现为混合性抑制,对游离酶的抑制常数和对酶-底物络合物的抑制常数分别为3.48和15.1mmol/L.展开更多
The inhibitory effects of methyl cinnamate on the monophenolase activity and diphenolase activity of tyrosinase were studied by enzymological kinetic method in Na2HPO4-NaH2PO4 buffer solution(pH=6.8) at 30 ℃.Methyl c...The inhibitory effects of methyl cinnamate on the monophenolase activity and diphenolase activity of tyrosinase were studied by enzymological kinetic method in Na2HPO4-NaH2PO4 buffer solution(pH=6.8) at 30 ℃.Methyl cinnamate was found to inhibit the monophenolase activity and diphenolase activity of tyrosinase.The methyl cinnamate concentration leading to 50 % inhibitory rate(IC50) were 0.61 mmol/L for monophenolase activity and 1.49 mmol/L for diphenolase activity,respectively.Methyl cinnamate coued extend the lag time of monophenolase.0.8 mmol/L of methyl cinnamate resulted in the lag time extension from 1.1 min to 3.2 min.The inhibition kinetics analyzed by Lineweaver-Burk plots indicated that methyl cinnamate was a noncompetitive inhibitor to diphenolase,and the inhibition constant KI for inhibitor binding with enzyme(E)was 0.66 mmol/L.展开更多
The microwave-assisted extraction(MAE)technology of tyrosinase inhibitor from batryticated silkworms was studied with the yield and the relative inhibitory activity against tyrosinase(RIAAT) of the extract used as eva...The microwave-assisted extraction(MAE)technology of tyrosinase inhibitor from batryticated silkworms was studied with the yield and the relative inhibitory activity against tyrosinase(RIAAT) of the extract used as evaluating indexes in the experiment.The effects of extraction variables,especially solvent concentrations,microwave power,the duration of microwave irradiation,materials-solvent mass ratio and material particle size on extraction efficiency were investigated.It was concluded that the optimal condition was two doses of microwave radiation(450 W) for 7 min with a mass ratio of 70 % ethanol to material by 8∶1.The extract of batryticated silkworms with 15.8 % yield and 66.7 % RIAAT was obtained after the extracted liquor was decoloured with active char,concentrated and then dried under vacuum.Compared with direct-heating extraction(DHE),MAE can shorten extracting duration,improve the yield and RIAAT of the extract.展开更多
文摘在25℃,pH=6.8的Na2HPO4-NaH2PO4缓冲体系中,采用酶动力学方法研究了香草醛对酪氨酸酶单酚酶和二酚酶活性的抑制效应.实验结果表明:香草醛对酪氨酸酶单酚酶和二酚酶活性均有抑制作用,其半数抑制浓度(IC50)约分别为2.7和4.1mmol/L;香草醛能明显延长单酚酶的迟滞时间,4 mmol/L香草醛能使迟滞时间由1.1 m in延长至3m in;Lineweaver-Burk图显示香草醛对二酚酶的抑制作用表现为混合性抑制,对游离酶的抑制常数和对酶-底物络合物的抑制常数分别为3.48和15.1mmol/L.
文摘The inhibitory effects of methyl cinnamate on the monophenolase activity and diphenolase activity of tyrosinase were studied by enzymological kinetic method in Na2HPO4-NaH2PO4 buffer solution(pH=6.8) at 30 ℃.Methyl cinnamate was found to inhibit the monophenolase activity and diphenolase activity of tyrosinase.The methyl cinnamate concentration leading to 50 % inhibitory rate(IC50) were 0.61 mmol/L for monophenolase activity and 1.49 mmol/L for diphenolase activity,respectively.Methyl cinnamate coued extend the lag time of monophenolase.0.8 mmol/L of methyl cinnamate resulted in the lag time extension from 1.1 min to 3.2 min.The inhibition kinetics analyzed by Lineweaver-Burk plots indicated that methyl cinnamate was a noncompetitive inhibitor to diphenolase,and the inhibition constant KI for inhibitor binding with enzyme(E)was 0.66 mmol/L.
文摘The microwave-assisted extraction(MAE)technology of tyrosinase inhibitor from batryticated silkworms was studied with the yield and the relative inhibitory activity against tyrosinase(RIAAT) of the extract used as evaluating indexes in the experiment.The effects of extraction variables,especially solvent concentrations,microwave power,the duration of microwave irradiation,materials-solvent mass ratio and material particle size on extraction efficiency were investigated.It was concluded that the optimal condition was two doses of microwave radiation(450 W) for 7 min with a mass ratio of 70 % ethanol to material by 8∶1.The extract of batryticated silkworms with 15.8 % yield and 66.7 % RIAAT was obtained after the extracted liquor was decoloured with active char,concentrated and then dried under vacuum.Compared with direct-heating extraction(DHE),MAE can shorten extracting duration,improve the yield and RIAAT of the extract.
