ASPARAGINASE-II OF SACCHAROMYCES-CEREVISIAE - GLN3 URE2 REGULATION OFA PERIPLASMIC ENZYME/

The production of some extracellular enzymes is known to be negatively affected by readily metabolized nitrogen sources such as NH4+ althoug h there is no consensus regarding the involved mechanisms. Asparaginas e II is a periplasmic enzyme of Saccharomyces cerevisiae encoded by th e ASP3 gene. The enzyme activity is not found in cells grown in either ammonia, glutamine, or glutamate, but it is found in cells that have been subjected to nitrogen starvation or have been grown on a poor sou rce of nitrogen such as proline. In this report it is shown that the f ormation of this enzyme is dependent upon the functional GLN3 gene and that the response to nitrogen availability is under the control of th e URE2 gene product. In this respect the expression of ASP3 is similar to the system that regulates the GLN1, GDH2, GAP1, and PUT4 genes tha t codes for glutamine synthetase, NAD-linked glutamate dehydrogenase, general amino-acid permease, and high affinity proline permease, respe ctively.