Determination of molecular weights and Stokes' radii of non‐denatured proteins by polyacrylamide gradient gel electrophoresis. 2. Determination of the size of stable and labile molecular weight variants of enzymes from plant sources

Abstract

AbstractUnder certain conditions in polyacrylamide gradient gel electrophoresis (PAGGE), a linear correlation between the logarithm of the size of calibration proteins (log MW or log Rs) and the square root of their migration distance (√D) can be observed; slope and intercept of the calibration curve depend on the duration of electrophoresis; linearity, however, is maintained over a wide range (4‐60 h, 200 V) (Rothe and Purkhanbaba, Electrophoresis 1982, 3, 33–42.) Using this method the reaction of plant isozyme systems penetrating a linear polyacrylamide (PAA) gradient gel was investigated: lactate dehydrogenase (LDH) from potato tubers behaves similarly to animal calibration proteins. The enzyme exhibits 3 subbands with molecular weights of 144 000, 150 000 and 156 000 (± 1.7 %), respectively. The enzyme system “shikimate oxidoreductase” (SORase) behaves significantly different: during PAGGE it splits into 2 major bands (∼60 000 and ∼110 000, respectively) consisting of several subbands. The results of our experiments show that SORase is present in vivo as a complex system. We believe that this complex is partly indentical with the so‐called pre‐chorismate complex.