Human insulin-like growth factor binding protein-6 is O-glycosylated.

Insulin-like growth factor binding protein-6 (IGFBP-6) is found in serum, cerebrospinal fluid and conditioned media from human fibroblasts. It has a marked preferential binding affinity for IGF-II over IGF-I. The present study demonstrates that IGFBP-6 purified from human cerebrospinal fluid is O-glycosylated but not N-glycosylated. Enzymatic deglycosylation does not alter the high affinity of IGFBP-6 for IGF-II (Ka 4.4 +/- 2.2 x 10(11) M-1) or its preference for IGF-II over IGF-I. The effect of glycosylation of IGFBP-6 on its secretion, in vivo stability or localization remains to be determined.