Enzymatic Synthesis of a Tetraglycosylceramide by a Galactosyltransferase from Rabbit Bone Marrow

A galactosyltransferase that transferred galactose from UDP-galactose to O-β-(N-acetyl)-glucosaminosyl (1 → 3)-O-β-galactosyl (1 → 4) glucosyl (1 → 1) ceramide to give galactosyl-O-β-(N-acetyl)glucosaminosyl (1 → 3)-O-β-galactosyl (1 → 4)-glucosyl (1 → 1) ceramide was detected in homogenates of rabbit bone marrow. The enzyme was present in the supernatant solution obtained after homogenization of rabbit bone marrow in the presence of Triton X-100 and centrifugation at 100,000 x g. The product of the reaction was isolated, purified, and analyzed for its constituents. It formed a precipitin line with anti-type XIV pneumococcal polysaccharide horse serum, and the line fused with that of tetraglycosylceramide derived from rabbit erythrocyte B active pentaglycosylceramide. UDP-galactose could not be replaced by galactose or galactose-1-P; the Km values were 5.0 x 10-4 m and 1.2 x 10-4 m for the triglycosylceramide and UDP-galactose, respectively.