Effect of PPX1 Inactivation on the Exopolyphosphatase Spectra in Cytosol and Mitochondria of the Yeast Saccharomyces cerevisiae

L. P. Lichko, N. A. Pestov, T. V. Kulakovskaya^*, and I. S. Kulaev

Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino 142290, Moscow Region, Russia; fax: (095) 956-3370; E-mail: alla@ibpm.serpukhov.su

^* To whom correspondence should be addressed.

Received May 27, 2002

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Inactivation of PPX1 encoding exopolyphosphatase PPX1 in Saccharomyces cerevisiae results in a change in the exopolyphosphatase spectrum in the yeast cells. In the PPX1-deficient strain, elimination of an ~45 kD exopolyphosphatase is observed in the cytosol, and activity of an exopolyphosphatase with molecular mass of ~830 kD increases fivefold. The latter activity differs greatly in properties from the low-molecular-mass enzyme of the parent strain. In the soluble fraction of the mutant mitochondria, exopolyphosphatase of ~45 kD characteristic of the soluble mitochondrial fraction in the parent strain is eliminated, and exopolyphosphatase with a molecular mass of ~440 to ~830 kD is found. On PPX1 inactivation, a membrane-bound form of mitochondrial exopolyphosphatase is unaffected in its activity level and properties. Therefore, the membrane-bound exopolyphosphatase of mitochondria and the high-molecular-mass enzyme of the cytosol of S. cerevisiae are not encoded by the PPX1 gene, unlike the soluble low-molecular-mass exopolyphosphatase of mitochondria, which is probably a product of this gene with a posttranslational modification. In the PPX1 mutant, exopolyphosphatase properties in the cell as a whole undergo modifications including the ability to hydrolyze polyphosphates (polyP) with different polymer degree.

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KEY WORDS: cytosol, mitochondria, soluble fraction, membrane-bound fraction, exopolyphosphatase, Saccharomyces cerevisiae

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