HUMAN CONJUGATED BILIRUBIN - ISOLATION, BIOSYNTHESIS, AND DIRECT MOLECULAR CHARACTERIZATION

  • 1 January 1980
    • journal article
    • research article
    • Vol. 26  (9) , 1323-1335
Abstract
Human conjugated bilirubin was prepared by isolation from fresh gallbladder bile and by biosynthesis using liver homogenates. The isolation protocol was modified after Lucassen and the in vitro synthesis was done with fresh liver homogenates in the presence of D-glucaro-1,4-lactone (a glucuronidase inhibitor). From direct analyses of these preparations with 270-MHz proton NMR and field-desorption mass spectrometry, a major conjugated bilirubin species in bile is apparently a diglucuronide, whereas in liver biosynthesis it is a diconjugate containing glucuronic acid and possible glucuronolactone co-esterified to the bilirubin backbone. If the glucuronolactone is present in the native biosynthetic material it is unknown whether it derives from glucuronic acid and, if so, whether lactonization occurs before or after the acid was esterified to form the conjugate.