Although about 50% of populations in developed countries have bile supersaturated with cholesterol, only a small proportion of these individuals develop gallstones. This fact suggested the existence of a biliary protein that inhibits cholesterol crystallization. Ohya et al. (1993) purified and characterized such a biliary glycoprotein which consists of a heterodimer with subunits of molecular weight 63 kilodaltons and 58 kilodaltons. Each of the subunits is characterized by an isoelectric point of 6.6 and shows comparable inhibitory activity. Deglycosylation of the subunits shows that they share a similar, perhaps identical polypeptide backbone of 35 kilodaltons. Differential subunit glycosylation alone may account for the apparent heterodimeric structure.
Ohya, T., Schwarzendrube, J., Busch, N., Gresky, S., Chandler, K., Takabayashi, A., Igimi, H., Egami, K., Holzbach, R. T. Isolation of a human biliary glycoprotein inhibitor of cholesterol crystallization. Gastroenterology 104: 527-538, 1993. [PubMed: 8425696] [Full Text: https://doi.org/10.1016/0016-5085(93)90423-a]