Purification and properties of malate dehydrogenase from Paracoccus denitrificans.

Affinity chromatography on immobilized Cibacron Blue (Matrex Gel Blue A) gel permeation chromatography on UltroPac TSK G 3000 SWG column and ion-exchange chromatography on "Mono Q" column were used to purify the malate dehydrogenase (MDH) from P. denitrificans to electrophoretic homogeneity. The last two purification steps were performed in FPLC system. The enzyme having a specific activity of about 2300 nkat/mg protein was obtained with an approximate 70% yield. MDH is a dimer with a molecular mass of 80,000 +/- 10,000 and an isoelectric point of 4.85 +/- 0.05. Absorption, fluorescence and CD-spectra were also measured and basic kinetic parameters were obtained for the homogeneous enzyme. The present paper also suggests the possibility of using the prepared enzyme for the determination of aspartate transferase (AST) in blood serum.