The enzyme polyphosphate kinase (ATP: Polyphosphate phosphotransferase EC 2.7.4.1) relating to the class of transferases was detected in the vacuoles of Saccharomyces carlsbergensis yeast. The direct ATP: Polyphosphate phosphotransferase reaction resulting in the synthesis of polyphosphates from ATP was shown to occur mainly in vacuoles. The localization of the reverse polyphosphate: ADP phosphatransferase reaction was not established in any of the subcellular yeast fractions studied. The activity of the direct reaction in the yeast protoplasts makes up about 1% of the reverse one, but in vacuoles it is significantly higher and makes up to 19%. Under activation of biochemical processes involved in the production of cell wall components by protoplasts, vacuolar polyphosphates work mainly in the direction of ATP synthesis at the expense of polyphosphates accumulated in vacuoles.