engleski

Partial purification and characterization of 5’-phosphodiesterase from barley malt rootlets

5’-Phosphodiesterase (PDE, orthophosphoric diester phosphohydrolase, EC 3.1.4.1) is widespread in animals, plants and microorganisms (1, 2). Although the biochemical properties of 5’-phosphodiesterases from various sources are somewhat different, there are three general features of most 5’-phosphodiesterases from plants (3): a) these enzymes hydrolyse polynucleotide chains from the 3’-end and release 5’-mononucleotides; b) the molecular weight of these enzymes is 100 kD or larger, and c) the pH optimum for the enzyme reaction ranges between 7 and 9. In this work, a 5’-phosphodiesterase activity from barley malt rootlets (Hordeum vulgare) has been partially purified by three steps fractional acetone precipitation (60 %, v/v). The enzyme was purified 37.75 folds over the crude extraction with an overall yield of 31.45 %. With thymidine 5’-monophosphate p-nitrophenyl ester as a substrate, it had an optimum pH of 8.9, maximum activity at 70 ^oC, and Km of 0.26 mM. In the presence of 10 mM Mg^+2 ions, the partially purified enzyme was activated up to 160 % of the original activity, while Zn^+2 ions, chelating agent (EDTA), NaN_3 and 5’-ribonucleotides were inhibitors of the enzyme activity. This enzyme was able to hydrolyze RNA and denaturated DNA efficiently, whereas native DNA was not a good substrate. The obtained 5’-phosphodiesterase enzyme preparation is an excellent catalyst for the production of 5’-ribonucleotides, known flavour enhancers, from spent brewer’s yeast. The enzyme preparation is also useful in applications where it is desirable to hydrolyze or remove nucleic acids and, it may be used to improve the filtrability of a microbial broth, too.

partial purification; 5’-phosphodiesterase; barley malt rootlets

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