Effect of Proline, Betaine and Some Other Solutes on the Heat Stability of Mitochondrial Enzymes

Abstract

When isolated plant mitochondria are heated, isocitrate dehydrogenase, malate dehydrogenase and fumarase lose activity at different rates. The rate of loss of activity of each enzyme is reduced if the mitochondria are heated in the presence of proline, betaine or some other solutes; protection by proline or betaine against heat inactivation is also evident with these enzymes when they are solubilized. NAD-isocitrate dehydrogenase in pea mitochondria and NADP-dependent isocitrate dehydrogenase of pea chloroplasts are also protected by proline and betaine against inactivation when the isolated organelles are heated.