PURIFICATION AND PARTIAL CHARACTERIZATION OF 2 THIOREDOXINS FROM STREPTOMYCES-AUREOFACIENS

Thioredoxins are low molecular weight proteins, which participate in a wide spectrum of biochemical reactions. Two thioredoxins from Streyto myces aureofaciens 3239 have been purified to homogeneity by a sequenc e of chromatography steps including chromatography on Sephacryl S-300, Phenyl Sepharose CL 4B and MonoQ HR 5/5. Thioredoxin activity clearly separates into two protein fractions on MonoQ HR 5/5 chromatography. Molecular weights determined by chromatography on Superose 12 KR 10/30 and sodium dodecyl sulphate polyacrylamide gel electrophoresis reveal ed M(r) similar to 10,500 for thioredoxin 1 (TR1) and M(r) similar to 11,000 for thioredoxin 2 (TR2). The isoelectric points of the two thio redoxins are different pI = 4.7 for TR1 and 5.6 for TR2, respectively. Both were effectively reduced with NADPH in reaction catalyzed by Ste ptomyces aureofaciens thioredoxin reductase. The specific activity of viewly for discovered TR2 is about 1/4 of the specific activity of TR1 . Both thioredoxins activate spinach NADPH-malate dehydrogenase, Activ ation of this enzyme by TR2 is only half effective than by TR1. The st ability of TR1 is high and similar to thioredoxins from other organism s unlike the activity of TR2 which is decreased during purification. T he proteins diversed in their contents in exponentialy growing myceliu m.