Carbon catabolite repression: not only for glucose

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Organisms prioritize glucose (preferred carbon source), repressing other carbon metabolism via catabolite repression.
• The regulation of "poor" carbon source utilization, especially in relation to each other, is less understood.
• Ethanol utilization in yeast Saccharomyces cerevisiae involves the enzyme alcohol dehydrogenase (ADH2).

Purpose of the Study:

• To investigate the regulatory mechanisms of "poor" carbon source utilization in Saccharomyces cerevisiae.
• To determine if acetate, a product of ethanol metabolism, influences ADH2 expression and ethanol utilization.
• To elucidate the site of acetate sensing (internal vs. external) and its role in carbon source hierarchy.

Main Methods:

• Enzyme assays to measure alcohol dehydrogenase activity.
• Gene expression analysis to study ADH2 regulation.
• Metabolic studies involving different carbon sources and acetate levels.
• Cellular localization studies for acetate sensing.

Main Results:

• Acetate, in addition to glucose, represses the expression of ADH2, inhibiting ethanol utilization.
• Acetate sensing occurs intracellularly, not through external medium detection.
• Saccharomyces cerevisiae exhibits a hierarchical utilization of "poor" carbon sources, influenced by acetate levels.

Conclusions:

• Acetate acts as an internal signal to regulate the utilization of ethanol, a "poor" carbon source.
• The findings reveal a more complex regulatory network for carbon source metabolism than previously appreciated.
• A hierarchy exists for "poor" carbon source utilization, involving intracellular acetate sensing.