Why are there different isozymes (isoenzymes)? (a) Because identical reactions may be performed in different cellular compartments, or under different pH, temperature optima (b) Because isoenzymes perform reactions using different coenzymes, increasing the flexibility of the cell (c) To respond to different concentrations in different organs (d) Due to genome duplications we may have more copies of similar enzymes, increasing the flux through a pathway (e) To perform the same reaction with different substrates and different products