Purification and structural comparisons of the cytosolic and mitochondrial fumarases from baker's yeast.

1. The cytosolic and mitochondrial fumarases (EC 4.2.1.2) from baker's yeast (Saccharomyces cerevisiae) have been purified to homogeneity. 2. Subunit molecular weights for the cytosolic and mitochondrial isoenzymes were 53,000 and 48,000 respectively. 3. Peptide maps obtained after digestion of the two isoenzymes with trypsin were almost identical but showed significant small differences. The same was true of peptide maps obtained after digestion with the glutamic acid-specific proteinase from S. aureus.