An extracellular 5′-nucleotidase with both monoesterase and diesterase activity from Micrococcus sodonensis

Abstract

A 5′-nucleotidase which has both monoesterase and diesterase activity has been isolated from the growth medium of Micrococcus sodonensis. The enzyme can be separated electrophoretically into three isoenzymes. The enzyme exhibited a pH optimum of 8.7, a molecular weight of approximately 115,000, and requires Mn 2+ for stability. It catalyzes the hydrolysis of the 5′-phosphate bond in both mononucleotides and dinucleotides, but has negligible activity with nucleic acids. The enzyme also catalyzes the hydrolysis of the synthetic substrate, p-nitrophenyl thymidine-5′-phosphate, to p-nitrophenyl phosphate and thymidine, the reaction used in the spectrophotometric assay of the enzyme. Its substrate specificity differentiates it from other nucleotidases which have been described, and indicates that it may be of use in the sequencing of oligonucleotides.