TAILIEUCHUNG - Báo cáo Y học: Characterization and regulation of yeast Ca2+-dependent phosphatidylethanolamine-phospholipase D activity

An unconventional phospholipase D (PLD) activity was identified recently in Saccharomyces cerevisiae which is Ca2+-dependent, preferentially hydrolyses phosphatidylethanolamine (PtdEtn) and phosphatidylserine and does not catalyse a transphosphatidylation with primary short-chain alcohols. We have characterized the cytosolic and membrane-bound forms of the yeast PtdEtn-PLD and examined the regulation of its activity under certain growth, nutritional and stress conditions. Both forms of PtdEtn-PLD activity were similarly activated by Ca2+ ions in a biphasic manner. Likewise, other divalent cations affected both cytosolic and membrane-bound forms to the same extent | Eur. J. Biochem. 269 3821-3830 2002 FEBS 2002 doi Characterization and regulation of yeast Ca2 -dependent phosphatidylethanolamine-phospholipase D activity Xiaoqing Tang Michal Waksman Yona Ely and Mordechai Liscovitch Department of Biological Regulation Weizmann Institute of Science Rehovot Israel An unconventional phospholipase D PLD activity was identified recently in Saccharomyces cerevisiae which is Ca2 -dependent preferentially hydrolyses phosphatidylethanolamine PtdEtn and phosphatidylserine and does not catalyse a transphosphatidylation with primary short-chain alcohols. We have characterized the cytosolic and membrane-bound forms of the yeast PtdEtn-PLD and examined the regulation of its activity under certain growth nutritional and stress conditions. Both forms of PtdEtn-PLD activity were similarly activated by Ca2 ions in a biphasic manner. Likewise other divalent cations affected both cytosolic and membrane-bound forms to the same extent. The yeast PtdEtn-PLD activity was found to interact with immobilized PtdEtn in a Ca2 -dependent manner. The partially purified cytosolic form and the salt-extracted membrane-bound form of yeast PtdEtn-PLD exhibited a similar elution pattern on size-exclusion chromatography coeluting as low apparent molecular weight peaks. PtdEtn-PLD activity was stimulated along with Spo14p Pld1p activity upon dilution of stationary phase cultures in glucose acetate and galactose media but PtdEtn-PLD activation was less pronounced. Interestingly PtdEtn-PLD activity was found to be elevated by w 40 in sed4 mutants at the restrictive temperature whereas in other sec mutants it remained unaffected. The activity of PtdEtn-PLD was reduced by 30-40 upon addition to the medium of inositol 75 M in either wild-type yeast or spo14D mutants and this effect was seen regardless of the presence of choline suggesting that transcription of the PtdEtn-PLD gene is down-regulated by inositol. Finally exposure of yeast .

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