Abstract
An alkaline phosphatase (ALPase) from Saccharomyces cerevisiae strain 257 was purified 345-fold with specific activity of 54 533 nmol × min−1 × mg protein−1 . It was shown to be a dimeric protein (apparent mol. wt. approx. 130 kDa) with optimum activity at pH 8.6 - 8.8 and good stability at 50 °C. The ALPase was a non-specific enzyme hydrolyzing a wide variety of monophosphate esters. The enzyme showed protein phosphatase activity and this activity was not Mg2+ - dependent in contrast to p-nitrophenyl phosphate (pNPP) activity. The Km value for pNNP hydrolysis was determined to be 2.2 × 10−5 м. Orthophosphate inhibited the enzyme in a competitive mode with the Ki of 2.3 x 10−4 м. Phosphate transfer of the ALPase is almost zero with all alcohols tested except for Tris.
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