Most organisms possess genetic variation for enzymes involved in basic metabolism, but the functional significance of this variation is poorly understood. The investigators are examining the function of enzyme variation at a number of levels of biological organization, including biochemical, metabolic, physiological and populational, to understand adaptive mechanisms thoroughly in a sea anemone, Metridium senile. Previous work has shown that there are differences in properties of variants for the carbohydrate-metabolizing enzyme glucosephosphate isomerase (Gpi) and that these differences result in alteration of carbohydrate metabolism. During the course of the present project the investigators will determine whether enzyme differences affect other levels of metabolism. Specifically, this phase of the project will investigate the modulation of lipid metabolism and additional portions of carbohydrate by metabolism Gpi variants. The working hypothesis is that differences in properties of Gpi variants contribute to adaptation to environmental temperature. Experiments will be conducted using radiolabeled compounds to determine whether modulation of carbohydrate metabolism in turn affects lipid synthesis. These experiments will provide essential information to test the hypothesis that natural selection by thermal environments is the cause for observed geographic variation in proportions of Gpi variants long the northeast coast of the US. The project will contribute to basic understanding of mechanisms by which organisms become genetically and metabolically adapted to environmental differences. Because enzyme-genetic variation is found in all living things, our results will shed light on a question of fundamental importance in understanding the process of adaptation. More specifically, the project will yield understanding of genetic aspects of temperature adaptation, of potential practical importance in determining likely consequences of human alterations of the thermal environment. The result may also shed fundamental light on the importance of small differences in enzyme properties for metabolic regulation.
