Polyphosphates and exopolyphosphatase activities in the yeast Saccharomyces cerevisiae under overexpression of homologous and heterologous PPN1 genes

The role of exopolyphosphatase PPN1 in polyphosphate metabolism in fungi has been studied in strains of Saccharomyces cerevisiae transformed by the yeast PPN1 gene and its ortholog of the fungus Acremonium chrysogenum producing cephalosporin C. The PPN1 genes were expressed under a strong constitutive promoter of the gene of glycerol aldehyde-triphosphate dehydrogenase of S. cerevisiae in the vector pMB1. The yeast strain with inactivated PPN1 gene was transformed by the above vectors containing the PPN1 genes of S. cerevisiae and A. chrysogenum. Exopolyphosphatase activity in the transformant with the yeast PPN1 increased 28- and 11-fold compared to the mutant and parent PPN1 strains. The amount of polyphosphate in this transformant decreased threefold. Neither the increase in exopolyphosphatase activity nor the decrease in polyphosphate content was observed in the transformant with the orthologous PPN1 gene of A. chrysogenum, suggesting the absence of the active form of PPN1 in this transformant.