isolation of enzyme transketolase from human erythrocytes: the characterization of its quaternary structure

ABSTRACT

Human erythrocyte transketolase [sedoheptulose-7-phosphate D-glyceraldehyde-3-phosphate, glycolaldehyde transferase, E. C. 2.2.1.1.] has been isolated from erythrocytes with a specific activity of 59.84 U/mg. SDS-PAGE and SE-.HPLC were used both as a measure of purity and as a preparative mean to obtain a higher degree of purity. Four protein bands corresponding to molecular weights of 32,000, 39,000, 43,000 and 60,000 were obtained in electrophoresis and SE-HPLC preparations. Activity measurements on the two fractions obtained from SE-HPLC that contained a monomer with the molecular weight of 32,000 and a dimeric fraction with the molecular weight of 60,000 showed that the monomeric form of the enzyme displays activity in the presence and absence of the TPP and Mg[II]. This activity was measured to be 14.76 U/mg in the absence of TPP and Mg[II], and 40.24 U/mg in the presence of the cofactors. The dimeric form showed an activity of 58.84 U/mg in the presence of the cofactors