Asparaginase II of Saccharomyces cerevisiae: selection of four mutations that cause derepressed enzyme synthesis

Area of Science:

• Molecular Biology
• Yeast Genetics
• Enzyme Regulation

Background:

• Asparaginase II is an important enzyme in Saccharomyces cerevisiae.
• Understanding the regulation of asparaginase II synthesis is crucial for metabolic studies.
• Previous studies identified mutations (asp3, asp6) leading to complete loss of enzyme activity.

Purpose of the Study:

• To identify and characterize mutations in Saccharomyces cerevisiae that lead to derepressed synthesis of asparaginase II.
• To investigate the genetic linkage of these new mutations with each other and with previously known mutations.

Main Methods:

• Employed a positive selection strategy to isolate mutations.
• Utilized genetic mapping techniques to assess linkage between mutations.
• Performed allelism tests to determine if mutations affect the same or different genes.

Main Results:

• Successfully isolated four distinct mutations (and1, and2, and3, and4) causing derepressed asparaginase II synthesis.
• These mutations were found to be unlinked to each other and to previously identified loss-of-function mutations (asp3, asp6).
• The and4 mutation was identified as allelic to gdh-CR, a mutation known to affect multiple nitrogen catabolism enzymes.

Conclusions:

• New genetic loci controlling asparaginase II synthesis in Saccharomyces cerevisiae have been identified.
• The findings suggest complex regulatory mechanisms for asparaginase II, involving genes distinct from those causing complete activity loss.
• The allelism of and4 with gdh-CR indicates a potential link between asparaginase II regulation and broader nitrogen metabolism pathways.