Masuda H, Heirwegh K P
Gastroenterol Jpn. 1979 Aug;14(4):312-5. doi: 10.1007/BF02774227.
In order to investigate the origin of unconjugated bilirubin in bile, beta-glucuronidase activity in rat and human bile was determined at various pH. beta-Glucuronidase in rat and human bile had their optimum pH at 5.5 when phenolphthalein glucuronide and delta 1-azopigment were used as substrate, and at 6.0 when bile itself was incubated. In human and rat bile the hydrolysis was suppressed to a minimum at each physiologic pH. However, human bile shows remarkable hydrolysis in alkaline pH (7.5--8.0). On the other hand, when delta 1-azopigment was incubated in various buffers, several per cent of delta 1-azopigment were hydrolyzed non-enzymatically in neutral to alkaline pH. Thus, it was suggested that enzymatic and nonenzymatic hydrolysis contributes to the existence of unconjugated bilirubin in bile.
为了研究胆汁中未结合胆红素的来源，在不同pH值下测定了大鼠和人胆汁中的β-葡萄糖醛酸酶活性。当以酚酞葡萄糖醛酸苷和δ1-偶氮色素作为底物时，大鼠和人胆汁中的β-葡萄糖醛酸酶在pH 5.5时活性最佳，而当胆汁自身进行孵育时，在pH 6.0时活性最佳。在生理pH值下，人和大鼠胆汁中的水解作用均被抑制到最低程度。然而，人胆汁在碱性pH值（7.5 - 8.0）下会发生显著水解。另一方面，当δ1-偶氮色素在各种缓冲液中孵育时，在中性至碱性pH值下，有百分之几的δ1-偶氮色素会发生非酶促水解。因此，提示酶促水解和非酶促水解都与胆汁中未结合胆红素的存在有关。
