AMINO-ACID-COMPOSITION OF PYRUVATE-KINASE M-2 ISOENZYME VARIANTS FROMRAT-LIVER AND MORRIS HEPATOMA-7777

Cytosolic fractions B (salted out between 51-70% ammonium sulphate sat uration) from rat liver and Morris hepatoma 7777, containing pyruvate kinase (EC 2.7.1.40) Mt isoenzymes, were purified by affinity chromato graphy on Blue Sepharose CL-6B. When compared by polyacrylamide gel el ectrophoresis at pH 8.3, all three M-2 pyruvate kinase variants from M orris hepatoma 7777 had lower mobilities (alpha(2), beta(2), gamma(3)) than the three corresponding variants (alpha(1), beta(1), gamma(2)) f rom normal rat liver. Using an automatic amino-acid analyser, signific ant differences in selected aminoacid content have been found in corre sponding highly purified gamma(3) and gamma(2) variants from Morris he patoma and normal rat liver, respectively. The gamma(3)-variant of the Morris hepatoma M-2 isoenzyme had twice the amount of L-tyrosine and L cysteine, and a content of L-serine higher by 20% than the correspon ding gamma(2) variant of the normal rat liver Mt isoenzyme. It contain ed, however, significantly less dicarboxylic amino acids which explain s its lower electrophoretic mobility. It showed also a decrease (by ab out 10%) in several other amino-acid content, corresponding to a 10% d ecrease in the tumour enzyme molecular mass.