没食子酸衍生物对蘑菇酪氨酸酶的抑制机理

蘑菇褐变过程主要是由于其酪氨酸酶的催化作用引起的，寻找该酶抑制剂在食品保鲜和储藏中的应用具有重要的意义．作者在实验中，发现没食子酸十二烷基酯和没食子酸香叶酯对蘑菇酪氨酸酶有较强的抑制作用，测定它们抑制蘑菇酪氨酸酶二酚酶的酶活力下降50％的抑制剂浓度（IC50）分别为1．55和0．25mmol／L．显示没食子酸香叶酯的抑制作用强度是没食子酸十二烷基酯的6倍．研究了这两种抑制剂对蘑菇酪氨酸酶的抑制作用动力学，结果表明：没食子酸十二烷基酯和没食子酸香叶酯对酶的抑制作用均表现为可逆反应，前者为反竞争性，其抑制常数KIS为0．636mmol／L；而后者为混合型，抑制常数KI和KIS分别为0．133和0．453mmol／L．

Inhibitory Mechanism of Gallate Derivatives on Mushroom Tyrosinase

Mushroom browning process is mainly caused by the effect of tyrosinase.It is of significantce to search tyrosinase inhibitors for the application on food anti-browning and storage.In the present work,we found that lauryl gallate(LG) and geranyl gallate(GG) have strong inhibitory effect on mushroom tyrosinase.The inhibitor concentrations leading to 50%(IC_(50)) of the enzyme activity lost were estimated to be 0.25 mmol/L and 1.55 mmol/L for them,respectively.The inhibitory potency of GG is as about six times as high as that of LG.Inhibitory kinetics of the enzyme by LG and GG was showed to be reversible reaction with remaining enzyme activity.LG was determined to be an uncompetitive inhibitor of the enzyme with the inhibition constant(K_(IS)) of 0.636 mmol/L;while GG belongs to be a mixed type inhibitor with the inhibition constants K_I of 0.133 mmol/L and K_(IS) of 0.453 mmol/L.