In most eucaryotic organisms, there are three isozymes of isocitrate dehydrogenase which vary in compartmental localization, oligomeric structure and cofactor specificity. In yeast, these enzymes also show different expression patterns under various culture conditions. Expressions of the mitochondrial NAD-specific (IDH) and cytosolic NADP-specific (IDP2) isozymes are repressed by growth on glucose whereas expression of the mitochondrial NADPspecific (IDP1) enzyme is constitutive. IDH is known to function in the TCA cycle but physiological functions for IDP1 and IDP2 have not been established. To assess metabolic functions of each isozyme, a complete collection of mutants was constructed by a genetic cross and subsequent sporulation and tetrad dissection. Extensive analysis of growth phenotypes for these mutants has clarified individual and cooperative functions. The availability of mutants with distinctive growth phenotypes allows expression and assessment of function of mutant and heterologous enzymes. In the current study, we expressed E.coli isocitrate dehydrogenase in yeast mitochondria and cytosol. The bacterial enzyme, which is NADP-specific, shares significant identity in primary structure with the two IDH subunits but not with the yeast NADP-specific isozymes. We found that the E.coli enzyme can not replace IDH for function in the TCA cycle but that it can replace NADP-specific isozymes in production of alpha-ketoglutarate.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology