Exostoses Like Protein 1 (EXTL1)

EXTL1 is a member of the multiple exostoses (EXT) family of glycosyltransferases, which function in the chain polymerization of heparan sulfate and heparin. The encoded protein harbors alpha 1,4- N-acetylglucosaminyltransferase activity, and is involved in chain elongation of heparan sulfate and possibly heparin.Various results suggested that EXTL3 is most likely involved in both chain initiation and elongation, whereas EXTL1 is possibly involved only in the chain elongation of heparan sulfate, and perhaps of heparin as well. Thus, the acceptor specificities of the 5 family members are overlapping but distinct, except for EXT1 and EXT2, which have the same specificity. Thus, all of the 5 cloned human EXT gene family proteins harbor glycosyltransferase activities, which probably contribute to the synthesis of heparan sulfate and heparin.