THREONINE DEHYDRATASE OF BACILLUS LICHENIFORMIS .2. REGULATION DURING DEVELOPMENT

The specific activity of the enzyme threonine dehydratase (threonine hydrolyase (deaminatng), EC 4.2.1.16) of Bacillus licheniformis decreases rapidly at the end of growth to a 4-fold lower level where it remains during development. The high specific activity of the enzyme is believed to be dependent on the maintenance of the physiological state that exists in growing cells. Experimental conditions that maintain this physiological state (addition of glucose or chloramphenicol) will prevent the decrease in specific activity of the enzyme, whereas conditions that allow the depletion of intracellular nutrients (mitomycin C) or mimic this effect (anaerobic shock) will cause a decrease in the specific activity of the enzyme. l-Isoleucine added to the medium can prevent the initial increase in specific activity. Other than the change is specific activity, no differences in physical or kinetic properties can be observed for the enzyme isolated from cells at different stages of the life cycle. Quantitation of the enzyme protein by an immunological procedure indicates that the amount of enzyme protein is constant per unit weight of cells during all phases of the life cycle of the organism. It is postulated that the variation in the specific activity of the enzyme is related to the metabolic activity of the cell. © 1968.