Examining the Putative Antioxidant Properties of Proline in Saccharomyces cerevisae

by Cali Reiling
Faculty advisor: Dr. Brian Lenzmeier

 There are many diseases associated with cellular damage caused by reactive oxygen species (ROS), including Alzheimer’s, Parkinson’s, diabetes, cancer and aging in general.1  High levels of the amino acid proline have been shown to protect cells from the damaging effects of ROS, but it is not known how proline exerts these anti-oxidant effects.  The enzymes catalase and peroxidase are made by cells to convert ROS into oxygen and water.  I have been examining the role that proline might play in the regulation of these enzymes.  We examined two potential mechanisms for proline’s antioxidant properties.  In our first set of experiments we added proline to either purified catalase or peroxidase to determine if proline had an allosteric affect on enzymatic activity. We found that proline did not significantly affect the activity of purified catalase or peroxidase, although there was a minor decrease in activity with the cow liver peroxidase enzyme. In our second set of experiments we examined peroxide processing activity in cell-free extracts from wild type BY4741 yeast cells grown in varying amounts of proline. We also examined the peroxide processing activity of yeast cell-free extracts made from strains lacking CAT A, CAT T, PUT 1, or PUT 3.  In all the cell extracts from the strains tested, proline caused a statistically significant increase in peroxide processing except in the CAT T knockout strain. These data suggest that proline may mediate its positive antioxidant effects through indirectly increasing the activity of Catalase T.

1Robert W. Taylor, Doug M. Turnbull. "Mitochondrial DNA Mutations in Human Diseases." Nature Reviews. Genetics. (2005): 389-401.