Quaternary Structure of Higher Plant Glyceraldehyde-3-Phosphate Dehydrogenases
- 1NAD(P)+-induced changes in the aggregational state of prepurified NADP-linked glyceraldehyde-3-phosphate dehydrogenase (EC 22.214.171.124) were used to isolate the enzyme from Spinacia oleracea, Pisum sativum and Hordeum vulgare. Each of the three plant species contains two separate isoenzymes. Isoenzyme 1 (fast moving during conventional electrophoresis) precipitates with the ammonium sulfate fraction 55–70% saturation. It shows two separate subunits in dodecylsulfate gels, which are probably arranged as A2B2 in the native enzyme molecule. Isoenzyme 2 (slow moving during conventional electrophoresis) precipitates with the ammonium sulfate fraction 70–95%. It contains a single subunit of the same Mr as subunit A in isoenzyme 1 and is apparently a tetramer (A4). The molecular weights of subunits A/B for spinach, peas and barley were determined as 38000/40000, 38000/42000 and 36000/39000 respectively.
- 2The NAD-specific glyceraldehyde-3-phosphate dehydrogenase (EC 126.96.36.199) was purified from Spinacia oleracea and Pisum sativum by affinity chromatography on blue Sepharose CL-6B. The enzyme from both plant species is shown to be a tetramer of subunits with Mr 39000.
- 3The present findings contrast with heterogeneous results obtained previously by other authors. These results suggested that there are considerable interspecific differences in the quaternary structure of glyceraldehyde-3-phosphate dehydrogenases from higher plants.