Regulation of GHD3: redundant pathway of glutamate biosynthesis in Saccharomyces cerevisiae

AVENDAÑO, A.; RIEGO, L.; GONZALEZ, A.

Universidad Simón Bolivar. Caracas, Venezuela.

Congreso; III Congreso Latinoamericano de Micología; 1999

Asociación Latiniamericana de Micología

The genes GDH1, GDH3 encode for two NADP-dependent glutamate dehidrogenases (NADP-GDH), involved in the glutamate biosynthesis in S. cerevisiae. We have studied the physiological role that each one of this two pathways plays in glutamate biosynthesis. In order to analyze the transcriptional regulation of GDH3, a 1230 pb PCR product of the upstream region of GDH3, the putative promoter of this gene, was fused in frame to the Lac-Z gene. The fusion plasmid, (pGDH3), was used to transform various strains harboring pertinent mutations. Our results suggest that GDH3p and not GDH1p constitutes the main pathway of the glutamate biosynthesis during diauxic and stationary growth phases. Our study has also shown that GDHI and GDH3 expression are controled by different transcriptional factors. Taken together our results indicate, that GDH1p and GDH3p participate in glutamate biosynthesis under different physiological conditions thus demonstrating that the presence of two NADP-GDH isozymes does not result in physiological redundancy, and that each one of this enzymes has a particular role.