The significance of l-proline for oxidative metabolism in the flight muscles of the Colorado beetle, Leptinotarsa decemlineata

Abstract

1. 1.Isolated Colorado beetle flight muscle mitochondria oxidize proline at a much higher rate than mitochondria obtained from other insects. They also oxidize proline more effectively than any other physiological substrate. Moreover, proline oxidation by Colorado beetle mitochondria is perfectly coupled and contributes to a highly efficient oxidative phosphorylation. 2. 2.During flight muscle development, the rate of proline oxidation increases relative to the rate of pyruvate oxidation. 3. 3.Proline is the most abundant free amino-acid in extracts from thoracic tissue. The free proline concentration is high enough to assure maximal proline oxidation in vivo. 4. 4.Proline stimulates the incorporation of [ 14C]leucine into the proteins of isolated Colorado beetle mitochondria. Other physiological substrates are far less effective in this respect. 5. 5.From these data we conclude that proline plays an important role in the oxidative metabolism of the flight muscles of the Colorado beetle.