B4GALT6 (Beta-1,4-galactosyltransferase 6) is an enzyme that plays a key role in the biosynthesis of glycosaminoglycans (GAGs) — complex carbohydrates found in proteoglycans. Located mainly in the Golgi apparatus, it catalyzes the transfer of galactose from UDP-galactose to core proteins, initiating the formation of GAG chains such as chondroitin sulfate.