Characterization and properties of pig liver transketolase.

Some properties of homogeneous transketolase (sedoheptulose-7-phosphate: D-glyceraldehyde-3-phosphate glycolaldehydetransferase, EC 2.2.1.1) from pig liver were studied. It was shown that the pH optimum of the transketolase reaction lies within the range of 7.8-8.2; the isoelectric point is at pH 7.6-7.8. The molecular weight of transketolase is 138 000 +/- 3000 as determined by the sedimentation equilibrium method. The enzyme molecular is a tetramer of the alpha 2 beta 2 type. The molecular weights of the alpha- and beta-subunits determined by polyacrylamide gel in the presence of sodium dodecyl sulphate are 52 000-56 000 and 27 000-29 000, respectively. Transketolase contains about 2 mol of thiamine pyrophosphate per mol of protein and does not require metal ions for its catalytic activity.