針對醣苷水解酶發展具有親和力與選擇性之抑制劑

Abstract

葡萄糖醛酸基化是人體主要的藥物代謝反應。腸道菌的β-葡萄糖醛酸酶(GUS) 會水解葡萄糖醛酸化的代謝物，在腸道中釋放出有毒性的醣苷配基，導致腸道的損傷。例如癌症化療藥物CPT-11被共生菌GUS在腸道中將其重新活化，所引發的腹瀉便是常見的劑量限制性毒性。選擇性的抑制細菌GUS而不必殺死菌群就能夠減輕這些副作用。uronic isofagomine是一個強的GUS抑制劑，但對於細菌與人類GUS不具備選擇性。我們設計與合成的一系列uronic isofagomine衍生物，可廣效的抑制多種細菌GUS，且對於人類GUS的選擇抑制比最多可達23378倍。這個選擇性與抑制劑延伸出的碳鏈所能作用到的醣苷配基結合位置 (Loop 3, Loop 5) 之胺基酸有關。與人類GUS不同，腸道菌GUS的醣苷配基結合位置以疏水性胺基酸為主，因此隨著抑制劑碳鏈的增長能獲得更多的疏水作用力。uronic isofagomine衍生物能夠通透入E. coli細胞內進行抑制，並且不會造成毒殺。我們進一步以小鼠動物模型證實了，口服這類衍生物能抑制腸道內之GUS活性，且不會傷害腸道組織。本研究首度以合理設計的方式，取得了具有親和力與選擇性的GUS抑制劑。藉由發展腸道菌的選擇性抑制劑將有助於避免藥物的代謝受到細菌酵素的干擾，而提升用藥的效率與安全性。

Glucuronidation is a major drug-metabolizing reaction in humans. Glucuronidated metabolites are hydrolyzed by intestinal bacterial β-glucuronidase (GUS) and release their toxic aglycones in intestines, resulting in intestinal damage. Diarrhea is a common dose-limiting toxicity caused by symbiotic bacterial GUS that reactivate cancer chemotherapeutic CPT-11 in the gut. Selective inhibition of bacterial GUS without killing microbiota alleviates these side effects. Although uronic isofagomine is a strong GUS inhibitor, while suffers from lack of selectivity. The derivatives of uronic isofagomine we designed and synthesized inhibit bacterial GUSs broadly. The human/E. coli GUS selectivity ratio reaches 23378. The selectivity was based on amino acids of aglycone binding site that alkyl chains of inhibitors interact with. Different from human GUS, bacterial GUSs possess more hydrophobic amino acids in aglycone binding site. The derivatives of uronic isofagomine shows effective against GUS in living E. coli cells and did not kill the bacteria. We further validated the ability of inhibitors to disrupt GUS activities in gut by mouse model.