对香豆酸、阿魏酸和低聚糖阿魏酸酯对酪氨酸酶的抑制效果

通过测定酶的稳态活力、迟滞时间和动力学参数,研究对香豆酸、阿魏酸及低聚糖阿魏酸酯对酪氨酸酶的抑制效果。结果表明,3种物质对酪氨酸酶单酚酶活性均有抑制作用,其中对香豆酸的抑制作用最强,其次为低聚糖阿魏酸酯和阿魏酸。对香豆酸、低聚糖阿魏酸酯和阿魏酸对单酚酶的IC_(50)值分别为0.75,3.20,9.30 mmol/L。对香豆酸和阿魏酸抑制二酚酶活性,IC_(50)值分别为4.3,12.7mmol/L;但低聚糖阿魏酸酯对二酚酶活力没有影响。对香豆酸能明显延长单酚酶反应的迟滞时间,阿魏酸影响很小,而低聚糖阿魏酸酯则缩短迟滞时间。动力学研究结果显示,阿魏酸和低聚糖阿魏酸酯对单酚酶的抑制作用表现为混合性抑制,而对香豆酸为竞争性抑制。

The inhibitory effect on tyrosinase from p-coumaric acid, ferulic acid and feruloylated oligosaccharides

This study investigated the inhibitory effects of p-coumaric acid, ferulic acid and feruloylated oligosaccharides on catalytic activities of tyrosinase by analysising tyrosinase steady state activity and enzyme kinetics. The results showed that the three compounds were found to efficiently inhibit tyrosinase monophenolase activities. The p-Coumaric acid was the strongest inhibitor followed by feruloylated oligosaccharides and ferulic acid, with the IC₅₀ value of 0.75, 3.20, 9.30 mmol/L respectively. Moreover, p-coumaric acid and ferulic acid were found to inhibit the activities of diphenolase with IC₅₀ value of 4.3, 12.7 mmol/L respectively; however, feruloylated oligosaccharides showed no inhibitory effect on diphenolase activity. p-Coumaric acid increased the lag time of monophenolase activity, but ferulic acid showed little effect; while feruloylated oligosaccharides reduced the lag time of monophenolase activity. Enzyme kinetics analysis indicated that p-coumaric acid is a competitive inhibitor of the monophenolase, while ferulic acid and feruloylated oligosaccharides showed a mixed inhibitory effect.