Muscle phosphofructokinase deficiency in man: expression of the defect in blood cells and cultured fibroblasts.

Using specific immunoprecipitation of M-type phosphofructokinase and assay of immunoprecipitate enzyme activity, it was possible to detect some M-type enzyme in normal blood cells and fibroblasts, although this isoenzyme represents a very small part of total phosphofructokinase. White blood cells and cultured fibroblasts from a patient with hereditary muscle phosphofructokinase deficiency showed normal phosphofructokinase activity and electrophoretic pattern; direct immunoneutralization results were also normal. Nevertheless, it was possible to prove the defect in these cells using the immunoprecipitation method: no active immunoprecipitates could be obtained with anti M-type antibody. The patient's red blood cells had a reduced phosphofructokinase activity which was only neutralized by anti L-type antiserum. The purification of partially deficient red cell phosphofructokinase confirmed that this enzyme only consisted of L-type subunits while, under normal conditions, both L- and M-type subunits are observed. The possibility of detecting specific enzyme defects in apparently non-affected cells could be of practical importance, especially in prenatal diagnosis.