HUMAN INSULIN-LIKE GROWTH-FACTOR BINDING PROTEIN-6 IS O-GLYCOSYLATED

Insulin-like growth factor binding protein-6 (IGFBP-6) is found in ser um, cerebrospinal fluid and conditioned media from human fibroblasts. It has a marked preferential binding affinity for IGF-II over IGF-I. T he present study demonstrates that IGFBP-6 purified from human cerebro spinal fluid is O-glycosylated but not N-glycosylated. Enzymatic degly cosylation 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 e ffect of glycosylation of IGFBP-6 on its secretion, in vivo stability or localization remains to be determined.