基于酪氨酸酶抑制活性的潜在美白剂比较与评价

Comparative evaluation of potential tyrosinase inhibitors as skin-whitening agents

摘要:

酪氨酸酶是黑色素代谢中的关键酶，具备抑制酪氨酸酶活性的物质可具有潜在美白活性。为此，本文以酪氨酸酶活性为指标，以曲酸（KA）为阳性对照，比较了N-乙酰神经氨酸（Neu5Ac）、透明质酸（HA）、烟酰胺单核苷酸（NMN）、烟酰胺（NAM）的抑制作用，并通过酶抑制动力学、光谱法、分子对接等技术，分析其对酪氨酸酶的抑制作用。结果表明：五种物质均可抑制酪氨酸酶活性，其中Neu5Ac（IC50=2.16 mmol·L-1）抑制酪氨酸单酚酶活能力仅次于KA（IC50=0.36 mmol·L-1）；Neu5Ac（IC50=2.73 mmol·L-1）抑制酪氨酸二酚酶活能力也仅次于KA（IC50= 1.48 mmol·L-1）。酶抑制动力学显示，Neu5Ac为非竞争型抑制，HA、NMN、NAM为混合型，KA为竞争型。紫外、荧光、红外光谱显示，五种物质通过改变酪氨酸酶疏水残基微环境，使酶构象改变，进而抑制酶活。分子对接显示，五种物质通过氢键和疏水相互作用结合到酶的疏水性空腔，尤其Neu5Ac的对接结合能最低（-7.1kcal·mol-1），结合稳定性最好。综上，相较而言，Neu5Ac以其较强的酪氨酸酶抑制活性，具有开发美白产品的潜在利用价值。

Abstract:

Tyrosinase is a key enzyme in melanin metabolism. Substances that inhibit tyrosinase activity can have potential whitening activity. In this paper, the inhibitory effects of N-acetylneuraminic acid (Neu5Ac), hyaluronic acid (HA), nicotinamide mononucleotide (NMN) and nicotinamide (NAM) on tyrosinase activity were compared with kojic acid (KA) as positive control, and the inhibitory effects on tyrosinase were analyzed by enzyme inhibition kinetics, spectroscopy and molecular docking. The results showed that all five substances could inhibit tyrosinase activity, among which Neu5Ac (IC50=2.16 mmol·L-1) was second only to KA (IC50=0.36 mmol·L-1). Neu5Ac ( IC50=2.73mmol·L-1) was also second only to KA (IC50=1.48 mmol·L-1). The enzyme inhibition kinetics showed that Neu5Ac was non-competitive inhibition, HA, NMN and NAM were mixed, and KA was competitive. UV, fluorescence, and infrared spectroscopy showed that the five substances changed the conformation of the enzyme by changing the microenvironment of the hydrophobic residues of tyrosinase, thereby inhibiting enzyme activity. Molecular docking showed that the five substances bound to the hydrophobic cavity of the enzyme through hydrogen bonds and hydrophobic interactions. In particular, Neu5Ac had the lowest docking binding energy (?7.1kcal·mol-1) and the best binding stability. In summary, in contrast, Neu5Ac has the potential to develop whitening products due to its strong tyrosinase inhibitory activity.