Amino-acid composition of pyruvate kinase M2 isoenzyme variants from rat liver and Morris hepatoma 7777.

Abstract

Cytosolic fractions B (salted out between 51-70% ammonium sulphate saturation) from rat liver and Morris hepatoma 7777, containing pyruvate kinase (EC 2.7.1.40) M2 isoenzymes, were purified by affinity chromatography on Blue Sepharose CL-6B. When compared by polyacrylamide gel electrophoresis at pH 8.3, all three M2 pyruvate kinase variants from Morris hepatoma 7777 had lower mobilities (alpha2, beta2, gamma3) than the three corresponding variants (alpha1, beta1, gamma2) from normal rat liver. Using an automatic amino-acid analyser, significant differences in selected amino-acid content have been found in corresponding highly purified gamma3 and gamma2 variants from Morris hepatoma and normal rat liver, respectively. The gamma3-variant of the Morris hepatoma M2 isoenzyme had twice the amount of L-tyrosine and L-cysteine, and a content of L-serine higher by 20% than the corresponding gamma2 variant of the normal rat liver M2 isoenzyme. It contained, however, significantly less dicarboxylic amino acids which explains its lower electrophoretic mobility. It showed also a decrease (by about 10%) in several other amino-acid content, corresponding to a 10% decrease in the tumour enzyme molecular mass.