联苯基甲醛与联苯基甲酸对蘑菇酪氨酸酶的抑制作用

Inhibition on Mushroom Tyrosinase Activity by Biphenylcarboaldehyde or Biphenylcarboxylic Acid

报道了联苯基甲醛与联苯基甲酸对蘑菇酪氨酸酶的抑制效应.研究结果表明:联苯基甲醛与联苯基甲酸对蘑菇酪氨酸酶均有明显的抑制作用,导致酶活力下降50%的抑制剂浓度(IC50)分别为86.5和860.0mmol/L,前者的抑制作用强度是后者的10倍.这两种抑制剂对蘑菇酪氨酸酶的抑制作用均表现为可逆过程,联苯基甲醛对酶的抑制作用为非竞争性,而联苯基甲酸是混合型.本文进一步测定它们的抑制常数KI和KIS,并加以比较.

Tyrosinase (1.14.18.1) is a metalloenzyme oxidase which catalyzes two distinct reactions of melanin synthesis:the hydroxylation of a monophenol and the oxidation of o-diphenol to the corresponding o-quinone. Biphenylcarboaldehyde and biphenylcarboxylic acid both can obviously inhibit the enzyme activity for the oxidation of L-DOPA. In the present work, the inhibition kinetics and mechanism of biphenylcarboaldehyde and biphenylcarboxylic acid on the enzyme for the oxidation of L-DOPA were studied. The results show that the inhibitory ability of biphenylcarboaldehyde is ten times that of biphenylcarboxylic acid. The inhibitor concentrations leading to 50% (IC_(50)) activity lost were estimated to be 86.5 mmol/L and 860.0 mmol/L, respectively. The inhibitions of tyrosinase by biphenylcarboaldehyde and biphenylcarboxylic acid both are a reversible reaction with remaining enzyme activity. The inhibitory mechanism of biphenylcarboaldehyde belongs to be noncompetitive while biphenylcarboxylic acid belongs to be a mixed type inhibitor. The equilibrium constants for those inhibitors binding with the enzyme had been determined.