Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090, Wien, Austria.
Universität Wien, Fakultät für Chemie, Institut für Anorganische Chemie, Währinger Str. 42, 1090, Wien, Austria.
Sci Rep. 2019 Mar 26;9(1):5183. doi: 10.1038/s41598-019-41261-7.
Mushroom tyrosinase abPPO4 is a commercially relevant polyphenol oxidase and has been being targeted for numerous inhibition studies including polyoxometalates (POMs). In the present work, its diphenolase activity was inhibited at pH 6.8 by a series of structurally related polyoxotungstates (POTs) of the α-Keggin archetype, exhibiting the general formula [XWO] in order to elucidate charge-dependent activity correlations. Kinetic data were obtained from the dopachrome assay and W NMR was applied to obtain crucial insights into the actual Keggin POT speciation in solution, facilitating a straightforward assignment of inhibition effects to the identified POT species. While [PWO] was completely hydrolyzed to its moderately active lacunary form H[PWO] (K = 25.6 mM), [SiWO] showed the most pronounced inhibition effects with a K of 4.7 mM despite of partial hydrolysis to its ineffective lacunary form H[SiWO]. More negative Keggin cluster charges of 5- and 6- generally resulted in preclusion of inhibitory efficacy as well as hydrolysis, but with the Ni-substituted cluster [PWO{Ni(HO)}] enzymatic inhibition was clearly restored (K = 9.7 mM). The inhibitory capacity of the structurally intact Keggin POTs was found to be inversely correlated to their net charge. The here applied speciation strategy is of utmost importance for any biological POM application to identify the actually active POM species.
蘑菇酪氨酸酶 abPPO4 是一种具有商业应用价值的多酚氧化酶，已经成为众多抑制研究的目标，包括多金属氧酸盐（POMs）。在本工作中，一系列结构相关的α-Keggin 型多钨酸盐（POTs）[XWO]在 pH 6.8 时抑制了其二酚酶活性，以阐明电荷依赖性活性相关性。动力学数据是通过多巴色素测定法获得的，W NMR 被应用于获得溶液中实际 Keggin POT 形态的关键见解，这有助于将抑制作用直接分配给所鉴定的 POT 物种。虽然 [PWO]完全水解为其中等活性的缺笼形式 H[PWO]（K = 25.6 mM），但 [SiWO]尽管部分水解为无效的缺笼形式 H[SiWO]，但仍表现出最显著的抑制效果，K 值为 4.7 mM。更负的 Keggin 簇电荷 5-和 6-通常会排除抑制效果和水解，但具有 Ni 取代簇的 [PWO{Ni(HO)}]，酶抑制作用明显恢复（K = 9.7 mM）。结构完整的 Keggin POT 的抑制能力与它们的净电荷呈反比。这里应用的形态策略对于任何生物 POM 应用来说都是至关重要的，以确定实际活性的 POM 物种。
