尽管它们释放相同的芳族糖苷配基,但是两个异构的芳基2-脱氧-2-氟-β-葡糖苷与β-葡糖苷酶的反应速率相差10 6倍。相反,当量的糖苷底物以基本相同的速率常数反应。通过对这些相同底物的非酶促(自发)水解的全面研究,洞悉了这些令人惊讶的速率差异的来源,其中测量了速率的大约10 5倍差异,从而阐明了差异是固有的,而不是原因造成的。与酶的特定相互作用。通过18排除了另一种亲核芳基取代机制导致更快的底物快速反应的可能性O标签研究。对这些速率差异的起源的进一步探索涉及X射线晶体结构的分析以及量子化学计算,这出乎意料地表明,基态去稳定化和过渡态稳定化作用几乎同等地促进了所观察到的反应性差异。这些研究突显了使用简单的参考平衡(例如p K a值)作为离开小组能力的量度的危险。
尽管它们释放相同的芳族糖苷配基,但是两个异构的芳基2-脱氧-2-氟-β-葡糖苷与β-葡糖苷酶的反应速率相差10 6倍。相反,当量的糖苷底物以基本相同的速率常数反应。通过对这些相同底物的非酶促(自发)水解的全面研究,洞悉了这些令人惊讶的速率差异的来源,其中测量了速率的大约10 5倍差异,从而阐明了差异是固有的,而不是原因造成的。与酶的特定相互作用。通过18排除了另一种亲核芳基取代机制导致更快的底物快速反应的可能性O标签研究。对这些速率差异的起源的进一步探索涉及X射线晶体结构的分析以及量子化学计算,这出乎意料地表明,基态去稳定化和过渡态稳定化作用几乎同等地促进了所观察到的反应性差异。这些研究突显了使用简单的参考平衡(例如p K a值)作为离开小组能力的量度的危险。
Chromogenic acridinone enzyme substrate compounds comprising 7-hydroxy-9H-acridin-2-one chromogens derivatized at the 7-hydroxy-position with an enzymatically-cleavable group and disubstituted at the 9-position with alkyl or aryl groups, which can be the same or different, preferably lower alkyl or phenyl, respectively, or together form a cyclohexa-2,5-diene-4-one residue or a 4-hydroxycycloxhexyl residue, and 7-hydroxy-1,3-dihalo-9,9-dimethyl-acridin-2-one intermediates useful for the preparation of the novel chromogenic acridinone enzyme substrate compounds and methods therefor. The enzymatically-cleavable group is a radical of a compound Y-OH comprising an enzyme-specific moiety which is capable of being cleaved by a specific enzyme wherein a deprotonated form of the chromogen is liberated having an absorbance maximum in basic solution which is substantially greater than the absorbance maximum of the chromogenic acridinone enzyme substrate compound to provide a distinct change in absorbance which can be accurately measured and correlated to the amount of enzyme present in a liquid test sample.
Remarkable Reactivity Differences between Glucosides with Identical Leaving Groups
作者:Tianmeng Duo、Kyle Robinson、Ian R. Greig、Hong-Ming Chen、Brian O. Patrick、Stephen G. Withers
DOI:10.1021/jacs.7b09645
日期:2017.11.8
18O-labeling studies. Further exploration of the origins of these rate differences involved analysis of X-ray crystal structures as well as quantum chemical calculations, which surprisingly revealed that ground state destabilization and transition state stabilizing effects contribute almost equally to the observed reactivitydifferences. These studies highlight the dangers of using simple reference equilibria
尽管它们释放相同的芳族糖苷配基,但是两个异构的芳基2-脱氧-2-氟-β-葡糖苷与β-葡糖苷酶的反应速率相差10 6倍。相反,当量的糖苷底物以基本相同的速率常数反应。通过对这些相同底物的非酶促(自发)水解的全面研究,洞悉了这些令人惊讶的速率差异的来源,其中测量了速率的大约10 5倍差异,从而阐明了差异是固有的,而不是原因造成的。与酶的特定相互作用。通过18排除了另一种亲核芳基取代机制导致更快的底物快速反应的可能性O标签研究。对这些速率差异的起源的进一步探索涉及X射线晶体结构的分析以及量子化学计算,这出乎意料地表明,基态去稳定化和过渡态稳定化作用几乎同等地促进了所观察到的反应性差异。这些研究突显了使用简单的参考平衡(例如p K a值)作为离开小组能力的量度的危险。