a School of Pharmacy and Medical Technology , Putian University , Fujian , China.
J Biomol Struct Dyn. 2018 Nov;36(14):3740-3752. doi: 10.1080/07391102.2017.1397059. Epub 2017 Nov 6.
Tyrosinase is the rate-limiting enzyme for controlling the production of melanin in the human body, and overproduction of melanin can lead to a variety of skin disorders. In this paper, the inhibitory kinetics of Dihydromyricetin (DHM) on tyrosinase and their binding mechanism were determined using spectroscopy, molecular docking, antioxidant assays, and chromatography. The spectroscopic results indicate that DHM reversibly inhibits tyrosinase in a mixed-type manner through a multiphase kinetic process with the IC of 849.88 μM. It is shown that DHM has a strong ability to quench the intrinsic fluorescence of tyrosinase mainly through a static quenching procedure, suggesting that a stable DHM-tyrosinase complex is generated. Molecular docking results suggest that the dominant conformation of DHM does not directly bind to the active site of tyrosinase. Moreover, the antioxidant assays demonstrate that DHM has powerful antioxidant and reducing capacity but does not have the ability to reduce dopachrome to L-DOPA. Interestingly, the results of spectroscopy and chromatography indicate that DHM is a substrate of tyrosinase but not a suicide substrate. The possible inhibitory mechanism is proposed, which will be helpful to design and search for tyrosinase inhibitors.
酪氨酸酶是人体黑色素生成的限速酶，黑色素的过度生成会导致多种皮肤疾病。本研究采用光谱学、分子对接、抗氧化测定和色谱等方法，确定了二氢杨梅素（DHM）对酪氨酸酶的抑制动力学及其结合机制。光谱结果表明，DHM 通过多相动力学过程以混合抑制方式可逆地抑制酪氨酸酶，其 IC 为 849.88 μM。结果表明，DHM 具有很强的猝灭酪氨酸酶内源荧光的能力，主要通过静态猝灭过程，表明生成了稳定的 DHM-酪氨酸酶复合物。分子对接结果表明，DHM 的优势构象并不直接与酪氨酸酶的活性位点结合。此外，抗氧化测定表明，DHM 具有强大的抗氧化和还原能力，但没有将多巴醌还原为 L-DOPA 的能力。有趣的是，光谱和色谱结果表明，DHM 是酪氨酸酶的底物，但不是自杀底物。提出了可能的抑制机制，这将有助于设计和寻找酪氨酸酶抑制剂。
