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pubmed:abstractText |
The cells of yeast P. guilliermondii contain specific p-nitrophenyl phosphatase (pNPPase), the level of which depends on the cells supply with inorganic phosphorus. Partially purified enzyme is activated by ions Mg2+, Co2+ and somewhat weaker -- by ions Fe2+. With the presence of Mg2+ the enzyme activity is inhibited by ions Cd2+, Zn2+, f-, Be2+, Cu2+, Mn2+, Ca2+, MoO42-, Fe3+, Fe2+, inorganic phosphate as well as by EDTA. A mixture ions Be2+ and F- causes a complete inhibition of the activity. Ions K+ and Na+ inhibit to some extent the enzymic activity, ATP removes the inhibitory effect of monovalent cations. Km of pNPPase is equal to 3.3-10(-4) M, the molecular weight determined by the method of gelfiltration is 60 000. The enzyme is the most active at 50 degrees C and pH 9,5 PNPPase does not manifest the phosphotranspherase activity in tris-HC1-buffer.
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