The relative activities attributable to the three phosphoglucomutase loci (PGM1, PGM,2 PGM3) in human tissues

SUMMARY 1. The isozymes attributable to the three phosphoglucomutase loci, PGM1;PGM2 and PGM3, have been separated by agarose‐acrylamide gel electrophoresis and their relative activities have been measured in a range of human tissues. 2. In most tissues except red cells and fibroblasts, 85–95 % of the total PGM activity is determined by the PGM1 locus, 2–15 % is contributed by the PGM2 locus and 1–2 % is determined by the third locus PGM3. 3. In fibroblasts the PGM3 isozymes are relatively much more active and account for nearly 7 % of the total PGM activity. 4. In red cells approximately equal amounts of the PGM1 and PGM2 isozymes occur but no PGM3 isozymes are found. 5. The atypical PGM isozyme pattern observed in red cells is probably a reflexion of in vivo stability differences between the three forms of PGM. In other tissues the PGM isozyme patterns are probably consequent upon differences in rates of synthesis or differences in the specific activities of the gene products.