Session: Undergraduate Research Posters: Biochemistry:

Thyroid peroxidase is a protein that plays an important role in the synthesis of thyroid hormones; mutations in the TPO gene can cause hypothyroidism, which affects many people around the world. The purpose of this experiment was to study the enzymatic activity of thyroid peroxidase (TPO) and determine if TPO maintains its functionality when it is produced in E. coli cells in a truncated form. This information can be used to determine if the modified TPO can be used for structural biology. Enzyme assays were run with both TPO and type I horseradish peroxidase. The assays were run with constant concentrations of the enzyme and guaiacol, and they were run with varying concentrations of hydrogen peroxide. The absorbance of each solution was collected over time at 470 nm with an ultraviolet-visible spectrophotometer. The concentration over time was then calculated using the Beer-Lambert law, and this data was used to create a plot of concentration versus time for each solution. The slopes of these plots were the reaction rates, and a software called Prism8 was used to plot the reaction rates against the concentration of hydrogen peroxide. This created a Michaelis-Menten plot, which was used to determine the K_M and V_max values for the assay. For the TPO assays, the average K_M value was 0.17 mM, and the average V_max value was 30.01 nM/min. For the type I horseradish peroxidase assay, the K_M value was 0.24 mM, and the V_max value was 1176 nM/min. The type I horseradish peroxidase assay required a significantly smaller concentration of enzyme than the TPO assay, and this indicates that type I horseradish peroxidase is a more efficient enzyme than TPO.

Dr. Natasha DeVore

Assistant Professor of Chemistry, Missouri State University

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