CHARACTERIZATION OF THE CHOLESTEROL CRYSTALLIZATION-PROMOTING LOW-DENSITY PARTICLE ISOLATED FROM HUMAN BILE

Background & Aims: Biliary concanavalin A-binding glycoprotein (CABG) contains cholesterol crystallization-promoting activity that is not ac counted for by the pronucleators that have been characterized in this fraction. The aim of this study was to isolate and characterize the mi ssing activity, Methods: Biliary glycoprotein was isolated using conca navalin A-Sepharose; Promoting activity in CABG was purified using den sity gradient ultracentrifugation. Results: Activity in CABG separated into two fractions at low (1.08) and high (1.29) density, which showe d di%ferent crystallization kinetics in a model bile. The high-density fraction had a late onset time (49.2 +/- 17.8 hours) but a high cryst al growth rate (13.4 +/- 5.2 mu g . mL(-1). h(-1)), The low-density fr action had a rapid onset: time (33.9 +/- 20.9 hours) but a stower grow th rate (6.5 +/- 3.8 mu g . mL(-1). h(-1)), The high-density fraction was not further characterized in this study, The low-density fraction contained solid particles consisting of lipid and very little protein, and the activity was fully pronase resistant, Delipidation of the low -density fraction removed ail activity, Conclusions: A potent pronase- resistant nucleation-promoting activity was activated from human bile and characterized, The low-density fraction may be responsible for the rapid nucleation in bile from typical patients with fast-nucleating g allstones.