Glycosaminoglycan sulfotransferases prepared from chick corneas were studied throughout embryonic development. Assay conditions were established using keratan sulfates (bovine cornea), heparan sulfates (human umbilicus), mixed isomer chondroitin sulfates (shark and whale cartilage), and chondroitin sulfates A (whale cartilage) as exogenous acceptors of 35S from phosphoadenylyl[35S]sulfate. The 35S-glycosaminoglycans formed with each exogenous substrate were characterized. The specific activities of corneal glycosaminoglycan sulfotransferases were determined throughout corneal development, using each exogenous acceptor as substrate. Effects of serum factors or thyroid hormones, or both, on the in vitro and in ovo activity of the enzymes also were investigated. The data with each exogenous acceptor indicate that glycosaminoglycan sulfotransferase specific activity changes only slightly during corneal development, and that embryonic chick sera of various ages contain substantial amounts of glycosaminoglycan sulfotransferase activity. Addition of exogenous glycosaminoglycan acceptors to preparations of corneal enzymes resulted in a 5- to 128-fold stimulation in the formation of 35S-glycosaminoglycans above endogenous levels. Dermatan sulfates and chemically desulfated keratan sulfates were not acceptors of 35S in these assays. The apparent K(m) of corneal glycosaminoglycan sulfotransferases for 3'-phosphoadenylyl[35S]sulfate (with keratan sulfates as exogenous acceptors) did not change significantly during corneal development. The 35S-glycosaminoglycan products formed in the standard sulfotransferase assays were identified as those expected for each exogenous substrate. Thyroid hormones or serum factors, or both, from various age embryonic chick sera did not significantly affect the in vitro glycosaminoglycan sulfotransferase activity of enzymes obtained from embryonic corneas or from chick sera. Thyroid hormones injected in ovo on Day 6 did not affect sulfotransferase activities found in Day 8 corneas. The degrees of sulfation of cornea glycosaminoglycans during development may be regulated by the availability of 3'-phosphoadenylylsulfate, rather than by the activity of sulfotransferase.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - 1978|
ASJC Scopus subject areas