Honors Program

Midway Honors

Date of Award


Thesis Professor(s)

Cecilia A. McIntosh

Thesis Professor Department

Biological Sciences

Thesis Reader(s)

Shivakumar P. Devaiah, David L. Hurley


Plant secondary products, which include the flavonoids, have a variety of roles in plant systems. Their roles include UV protection, antifeedant activity, pollinator attraction, stress response, and many others. Flavonoids also have effects on human physiology. Glucosylation is an important modification of many flavonoids and other plant secondary products. In grapefruit, glucosylation is important in the synthesis of the bitter compound naringin. Glucosyltransferases catalyze glucosylation reactions. Putative plant secondary product glucosyltransferases may be identified by the loosely conserved “PSPG box” amino acid sequence, and eleven have been isolated to date in Citrus paradisi. With current knowledge, however, biochemical characterization is the only way to determine with certainty the function of these enzymes. The hypothesis tested here is that PGT11 is a plant secondary product glucosyltransferase. To investigate the hypothesis, recombinant PGT11 (rPGT11) was expressed in yeast using the pPICZ A vector, and the enzyme was screened for glucosylation activity with flavonoid substrates of the flavanone, flavone, flavonol, and isoflavone subclasses. No significant activity was detected with any of the substrates screened; however, the tests should be repeated for verification. Flavonoids of other subclasses, phenolic acids, and other phenolics could be tested as well.

Document Type

Honors Thesis - Withheld

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