Purification and Characterization of Nucleotide-specific Phosphatases from Soybean Seeds

Abstract

Two kinds of nucleotide-specific phosphatases were separated chromatographically on a DEAE-Toyopearl 650 M column, and designated as NSP-I and -II. NSP-II was further purified to apparent homogeneity using both affinity and gel-filtration chromatography, but NSP-I purified by the same procedures was not homogeneous on polyacrylamide gel electrophoresis. NSP-I and -II had many similar features in molecular size, optimum pH, heat stability, and substrate specificity. The molecular weight of each enzyme protein was estimated to be approximately 45, 000 by molecular sieve chromatography. The optimum pH of each enzyme was 6.5 and showed activity in the wide pH range of 5-9. Neither enzyme hydrolyzed bis(p-nitrophenyl)phosphate, adenosine 2':3'-cyclic-monophosphate, or sugar phosphate, but both showed a marked preference for 5'-mononucleotides as substrate over p-nitrophenylphosphate.