[Identification of pyruvate kinase variants from red blood cells using trypsinization and electrophoresis]

Enzymopathies of pyruvate kinase (PK) are characterized by polymorphism. Nine distinct variants of the L-type from 10 patients suffering from nonspherocytic haemolytic anaemia have been identified by electrophoretic and kinetic methods. Typical changes of the electrophoretic mobility and kinetic properties of the L-type and K-type of PK can be produced by incubation of cytolysates and tissue homogenates in the presence of trypsin. After trypsinization the three distinct forms of the L-type from liver and erythrocytes show identical mobility. Trypsinization of haemolysates has proved to be a diagnostic tool for the differentiation of PK variants. The results also allow to distinguish whether the mutation is located in the region of the peptide chain which is split off by trypsin or not. In three cases the occurrence of two instead of one enzyme form after trypsinization indicates a double heterozygote heredity of PK-deficiency. The appearance of the K-type isoenzyme of PK in red blood cells may be considered as a physiological event during a limited period of erythropoiesis. The K-isoenzyme was found only in samples of red blood cells containing erythroblasts. One of the patients has shown a still unknown form of PK. The properties of this form resembled those of the major part of PK from human placenta.