Enzyme activities in flight and leg muscle of the dung beetle in relation to proline metabolism

Abstract

Relatively high activities of NAD-linked ‘malic’ enzyme (E.C.1.1.1.39) and alanine aminotransferase (E.C.2.6.1.2), predominantly or entirely mitochondrial, were found in the flight and coxal muscle of three species of dung beetle (Scarabaeidae: Coprinae). In this respect these muscles resembled the flight muscle of the tsetse fly Glossina morsitans, but contrasted with flight muscle from six other non-Coleopteran insect species examined. Flight and coxal muscle from the dung beetle Helicopris dilloni also contained high proline dehydrogenase and glutamate dyhydrogenase (E.C.1.4.1.2) activities, but particularly low activities of hexokinase (E.C.2.7.1.1), phosphofructokinase (E.C.2.7.1.11), aldolase (E.C.4.1.2.7) and lactate dehydrogenase (E.C.1.1.1.27). Mitochondrial preparations isolated from flight and leg muscle of H. dilloni respired more rapidly in the presence of proline than other added substrates. These results suggest the use of proline as a major direct energy source for both flight and non-flight muscle in Coprine beetles.