Kinetics of Synthesis and Secretion of [3h]leucine-, [3h]galactose- and [3h]mannose-labelled Myeloma Protein by Two Plasma-cell Tumours by Fritz Melchers

The kinetics of incorporation of leucine, galactose and mannose into intracellular and secreted myeloma protein, MOPC 21 IgG, and MOPC 46 K-type light chain, by cell suspensions of two myeloma plasma-cell tumours, MOPC 21 and MOPC 46, were similar. Radioactive galactose was incorporated to over 90% into galactose residues ofintracellular and secreted protein, mannose to over 90% into glucosamine and mannose residues of intracellular protein and to over 90% into glucosamine, mannose and fucose residues of secreted protein, but not into galactose residues. The results show that specific residues in the carbohydrate portion of myeloma proteins can be labelled by specific radioactive monosaccharides, and suggest that fucose residues are added, while myelomaprotein is in its final stage ofsecretion from the plasma cell. The kinetics of incorporation indicate at least three sequential precursor-product relationships between different intracellular forms and the secreted form of myeloma protein.