Adaptation of enzymes to temperature: myofibrillar adenosine triphosphatase from two terrestrial isopod species.

A comparison of the temperature profiles of the myofibrillar ATPase in Porcellio spinicornis and Metoponorthus pruinosus showed that Porcellio enzyme had a maximum activity between pH 6.8-7.2 at 9 degrees C, and that from Metoponorthus between pH 7.0-7.4 at 45 degrees C. The energy of activation for Porcellio enzyme was estimated to be 2.964 kcal/mol and that for Metoponorthus enzyme 9.91 X 10(-1) kcal/mol. The significance of these findings in relation to the natural habitats of these two species is discussed.