Many micro-organisms can use two-carbon compounds, like acetate or ethanol, as well as long chain fatty acids as sole carbon sources. Pathways and enzymes of the glyoxalate bypass, of fatty acid beta-oxidation, located in peroxisomes, as well as of the citric acid cycle located in mitochondria are required for the utilization of these carbon sources. The C6 zinc cluster protein FacB is required for acetate induction of enzymes involved directly in acetate metabolism, as well as of the glyoxalate bypass enzymes. We have previously shown that NADP-dependent isocitrate dehydrogenase activity is also regulated by FacB dependent acetate induction and by CreA mediated carbon catabolite repression in a similar manner to amdS, facA, acuD and acuE. The structural gene (idpA) has been cloned and shown to be regulated by CreA and FacB and also by induction by fatty acids. The predicted protein possesses both an N-terminal mitochondrial targeting signal and a C-terminal peroxisomal signal. This provides an interesting contrast with the situation in Saccharomyces cerevisiae where there are three genes encoding enzymes located in separate cell compartments. By the use of fluorescent protein (GFP, RFP and BFP) fusion constructs, idpA encoded NADP-isocitrate dehydrogenase has been found to be present in peroxisomes and mitochondria. The structure of the gene suggests the presence of two alternative start points of transcription that may result in the two different forms of the enzyme.
Full conference title:
21st Fungal Genetics Conference
- Fungal Genetics Conference 21st (2000)