We are in the process of clarifying some of the mechanisms whereby the level of trehalose (the major blood sugar) is maintained in the hemolymph of Phormia regina adults. Work will continue along previously supported lines: 1. Investigation of the kinetic properties of trehalose synthetase. The enzyme is very labile, so inhibitors and radioassay methods will be used to establish its activity in crude preparations. 2. Separation and description of the isozymes of trehalose. Gel electrophoretic methods will be used to isolate the enzymes from different tissues, and various properties of the isozymes will be compared. 3. An experimental analysis of the role of the humoral factors from the corpus cardiacum which may lead to alterations in the blood level of trehalose through their actions on the reactions directly involved with and surrounding the synthetic and degradative pathways. The activities of enzymes and the levels and rates of metabolism of storage compounds will be examined.