Inhibitory effect of 2-Hydroxy-4-isopropylbenzaldehyde on the activity of mushroom tyrosinase
会议名称：《第七届全国酶学学术讨论会》
会议日期：2004年
学科分类：0710[理学-生物学] 071001[理学-植物学] 07[理学]
关 键 词：mushroom tyrosinase 2-bydroxy-4-isopropylbenzaIdehyde inhibition kinetics
摘 要：Tyrosinase(EC 1.***.18.1) is known to be a key enzyme in melanin biosynthesis, involved in determining the color of mammalian skin and hair. Therefore, tyrosinase inhibitors have been established as important constituents of depigmentation agents. In this paper, salinaldehyde (a);cuminaldehyde (b) and 2-hydroxy-4-isopropylbenzaldehyde (c) were used as the samples to discuss the inhibitory effect on the activity of mushroom tyrosinase. The IC50 values for these three compounds were determined to be 75 μM, 2850μM and 12.5 μM, respectively, when L-3,4-dihydroxyphenylalanine (L-DOPA) was used as substrate. The inhibition kinetics analyzed indicated that compound (a) is a competitive inhibitor, compound (b) is an uncompetitive inhibitor of the tyrosinase. But the compound (c) shows mixed-type mechanism to the enzyme. The results were given in Table 1 for comparison. The result was analyzed that hydroxyl group at the ortho position of the aldehyde group contributed to highly inhibition activity, been seemed to form a quasi-six-membered ring with the nitrogen atom of the amino group through intramolecular hydrogen bonding. The Schiff base is largely governed by those factors affecting the stability of the carbon-nitrogen double bond. The electron-donating groups such as isopropyl at the para position seem to act not only by the inductive effect but to stable to the binding sites in the enzyme. So compound (c) was the most potent inhibitor of these three compouds. Compound (a) and (b) inhibit mushroom tyrosinase in different ways. Compound (a) competitively bind to the active site in the enzyme with substrate and is competitive inhibitor which only binds the free enzyme. Compound(b) only binds the ES complex rather than the free enzyme, contributing to uncompetitive inhibitory effect. And compound (c) consisted of hydroxyl group at the ortho position and isopropyl group at the para position, so it can combine with both free enzyme and enzyme-sustrate complex. It displayed co