The Estimation of Phosphatase in Yeast

For the determination of the phosphatase content of yeast many methods have been used (l-3). The usual method is to hydrolyze a glycerophosphate and measure the amount of inorganic phosphate liberated. King and Armstrong (4) have shown, however, that phenyl phosphate could be used as a substrate and the phenol det,ermined. To be satisfactory the method chosen must give a measurable amount of hydrolysis in as short a time as possible and must not require too much yeast. The advantages in using only a small amount of yeast are that there may be only limited amounts available and it reduces the amount,s of undesirable impurities frequently present. The method finally chosen was to measure the phenol liberated from a mixture of 10 mg. of yeast and 10 cc. of 0.01 M disodium phenyl phosphate, buffered with acet.ate veronal at pH 4.1, after 20 minutes at 37”. A summary of the experiments on which these choices are based follows.