Influence of compartmental localization on the function of yeast NADP+-specific isocitrate dehydrogenases.
Three differentially compartmentalized isozymes of isocitrate dehydrogenase (mitochondrial IDP1, cytosolic IDP2, and peroxisomal IDP3) in the yeast Saccharomyces cerevisiae catalyze the NADP(+)-dependent oxidative decarboxylation of isocitrate to form alpha-ketoglutarate. These enzymes are highly homologous but exhibit some significant differences in physical and kinetic properties. To examine the impact of these differences on physiological function, we exchanged promoters and altered organellar targeting information to obtain expression of IDP2 and IDP3 in mitochondria and of IDP1 and IDP3 in the cytosol. Physiological function was assessed as complementation by mislocalized isozymes of defined growth defects of isocitrate dehydrogenase mutant strains. These studies revealed that the IDP isozymes are functionally interchangeable for glutamate synthesis, although mitochondrial localization has a positive impact on this function during fermentative growth. However, IDP2, whether located in mitochondria or in the cytosol, provided the highest level of defense against endogenous or exogenous oxidative stress.
Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229, USA.
Veronica
V
Contreras-Shannon
Lee
L
McAlister-Henn
D002451:Cell Compartmentation / Q000502:physiology*; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007521:Isocitrate Dehydrogenase / Q000378:metabolism / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism / Q000502:physiology; D019344:Lactic Acid / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D009249:NADP / Q000378:metabolism*; D019301:Oleic Acid / Q000378:metabolism; D020675:Peroxisomes / Q000201:enzymology; D010957:Plasmids / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D014170:Transformation, Genetic
D007527:Isoenzymes; D011994:Recombinant Proteins; D019301:Oleic Acid; D019344:Lactic Acid; D018698:Glutamic Acid; D009249:NADP; D006861:Hydrogen Peroxide; D007521:Isocitrate Dehydrogenase; D005947:Glucose; D005990:Glycerol