Membrane-associated Glycosyl Transferases in Cotyledons of Pisum sativum: Differential Effects of Magnesium and Manganese Ions.

In crude particulate fractions isolated from pea (Pisum sativum) cotyledons, the transfer of radioactivity from GDP-[(14)C]mannose to glycolipid appears to be preferentially stimulated by Mn(2+) while the transfer to lipid-free residue is enhanced by Mg(2+). In contrast, the transfer of radioactivity from UDP-N-acetyl-[(14)C]glucosamine to glycolipid shows preferential stimulation by Mg(2+) while the transfer to lipid-free residue prefers Mn(2+). These results are accounted for by the differential stimulation by Mg(2+) and Mn(2+) of glycosyl transferases associated with subcellular membranes which were separated by isopycnic sucrose density centrifugation.