Adaptation of Drosophila enzymes to temperature. III. Evolutionary conservation in mitochondrial enzymes

The evolutionary behavior of two mitochondrial enzymnes (L-glycerol 3-phosphate:cytochrome c oxidoreductase E.C.1.1.1.95, alpha GPO, and L-malate: NAD+ oxidoreductase, E.C.1.1.1.37, m-MDH) obtained from several temperate and tropical Drosophila species was examined by comparing their catalytic properties, which related to temperature (Km-Ea-Q10-Thermostability). Mitochondrial alpha GPO or m-MDH obtained either from template or from tropical species was found to exhibit similar catalytic properties while for both cytosolic enzymes, the alpha GPDH and s-MDH, Km patterns were similar among species from the same thermal habitat and different thermal habitats. In combination with other observations reported in the literature these facts support the view that the function, and probably the structure, of mitochondrial enzymes are better conserved in evolution than those of the corresponding enzymes found in the cytosol. It is proposed that the relative invariance of the mitochondrial enzymes structure is probably linked to a necessary relative invariance of molecular interactions inside the mitochondrion.