Purification and Properties of a Disulfide Reductase Obtained from Achromobacter starkeyi

A disulfide reductase with characteristics different from those previously described in the literature was isolated from Achromobacter starkeyi. The enzyme was purified approximately 90-fold from cell-free extracts prepared with a Hughes press. Oxidized glutathione was the only natural substrate utilized by the partially purified enzyme. However, the enzyme showed a higher affinity and higher activity for the synthetic compound 5,5'-dithiobis(2-nitrobenzoic acid). The enzyme could utilize both NADH and NADPH as electron donors, but it was more active with NADPH. The optimum pH was 7.0, and the optimum temperature was about 28°. The enzyme was highly susceptible to the presence of divalent cations and iodoacetate, but arsenite and N-ethylmaleimide showed only a slight inhibitory effect. The enzyme was slowly inactivated when it was incubated in the presence of NADH or NADPH.