Abstract
In this pilot study we described the procedure of purifi cation for erythritol dehydrogenase (EDH) involved in the utilization of erythritol in M. smegmatis ATCC 20. Some properties of this enzyme were studied. This enzyme purifi ed from cytosolic fraction can be regarded as NAD+-depedent polyol (C3-5) dehydrogenase, for which the confi guration of –OH groups at C2-3 of polyols is either of D-erythro- or of L-threo-type. The Km constants for erythritol and L-erythrulose are 3.3 mM and 0.5 mM, respectively. The enzyme has optimum pH around 9.7 in glycine/NaOH buffer and at 6.5 in citrate/Na2HPO4 buffer in oxidative and reductive reactions, respectively. The characterized mycobacterial EDH is specifi c to pyridine nucleotides NAD+/NADH as coenzymes. The Km constants for NAD+ and NADH are 0.45 mM and 0.33 mM, respectively. Erythritol dehydrogenase from M. smegmatis ATCC 20 has pI 4.4–4.6 and molecular weight 160 kDa. Our results indicate that cysteine (amino acid with –SH group) and tryptophan are partially responsible for EDH activity. The inhibition activity of the characterized enzyme by tested chelators as EDTA, 1,10-phenantroline and TRIS indicate that the EDH is a metallprotein. A large similarity between the properties of inductive erythritol dehydrogenase from M. smegmatis ATCC 20 and constitutive ribitol dehydrogenase from M. smegmatis (M. butyricum) was discovered.
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