Simultaneous purification of L-malate dehydrogenase and L-lactate dehydrogenase from bovine heart by biomimetic-dye affinity chromatography

Two commercially important enzymes, L-lactate dehydrogenase (LDH) and L-malate dehydrogenase (MDH) were purified simultaneously from bovine heart, on an agarose affinity adsorbent. This adsorbent bears a dye-ligand composed of an anthraquinone chlorotriazine chromophore linked to a biomimetic terminal 4-aminophenyloxanylic acid moiety. The purification protocol exploited the biomimetic affinity adsorbent, in combination with a cross-linked agarose DEAE anion-exchanger. The procedure comprised a preliminary anion-exchange first step, for the separation of the three enzyme activities, mMDH, cMDH and LDH. In the second step, that of affinity chromatography, the unbound mMDH obtained from the first step, was purified by specific elution with NAD⁺/sulphite (22.5-fold purification, 55% step-yield). The procedure afforded mMDH preparation of specific activity approx. 1,300?u/mg (25?°C) at 45% overall yield, free of cytoplasmic MDH, glutamic-oxaloacetic transaminase (GOT) and fumarase. The LDH activity, which, bound to the anion-exchanger during the first step, was recovered from the adsorbent in 200?mM KCl, and finally purified by biomimetic-dye affinity chromatography (NAD⁺/sulphite elution) and a second ion-exchange chromatography step (elution with 200?mM KCl). The LDH preparation exhibited specific activity approx. 500?u/mg at 25?°C (content of impurities: pyruvate kinase and GOT were not detected; MDH, 0.01%).