As a safe substitute for hydroquinone, β-arbutin, a natural plant substance, and its synthetic counterpart, α-arbutin, are used in depigmentation formulations. However, there are debatable points regarding the impact of arbutin on tyrosinase and the pigmentation process. To shed light on this issue, the effects of Pyrus biossieriana leaves extract (PbLE) and β-arbutin, extracted from PbLE, on mushroom tyrosinase (MT) were comprehensively examined. The study was focused on cresolase activity as the characteristic reaction of a tyrosinase. Kinetics studies disclosed that β-arbutin can modulate MT monophenolase activity from inhibition to activation or vice versa. β-Arbutin inhibited l-tyrosine (LTy) oxidation at concentrations < 0.3 mM but it increased (more than 400%) the enzymatic oxidation of l-tyrosine at the concentrations > 0.3 mM. An opposite pattern (activation then inhibition) was observed when a synthetic substrate was used instead of LTy. Computational studies, focused on the heavy chain of MT, indicated that β-arbutin effect could be overruled by the enzyme's ability to provide the ligand with a non-specific binding site (MTPc). A plausible mechanism was presented to show the influence of MTPc on the substrate pose in the active site. The possible determinant correlation between the findings of this research and the current studies on human tyrosinase role in the pigmentation process has been presented.

作为对苯二酚的安全替代品，β-熊果苷（一种天然植物物质）及其合成对应物 α-熊果苷用于脱色配方。然而，关于熊果苷对酪氨酸酶和色素沉着过程的影响存在争议。为了阐明这个问题，综合研究了梨叶提取物 (PbLE) 和从 PbLE 中提取的 β-熊果苷对蘑菇酪氨酸酶 (MT) 的影响。该研究的重点是甲酚酶活性作为酪氨酸酶的特征反应。动力学研究表明，β-熊果苷可以调节 MT 单酚酶活性，从抑制到激活，反之亦然。β-熊果苷抑制l-酪氨酸（LTY）氧化在浓度<0.3毫米，但它增加（超过400％）的酶促氧化升-酪氨酸在浓度> 0.3毫米。当使用合成底物代替 LTy 时，观察到相反的模式（激活然后抑制）。专注于 MT 重链的计算研究表明，β-熊果苷的作用可能会被酶为配体提供非特异性结合位点 (MTPc) 的能力所推翻。提出了一种合理的机制来显示 MTPc 对活性位点中底物姿势的影响。本研究的结果与目前关于人类酪氨酸酶在色素沉着过程中的作用的研究之间可能存在决定因素相关性。