Hafsah Jamil

Date Approved

2018

Degree Type

Open Access Senior Honors Thesis

Department or School

Biology

First Advisor

Aaron Liepman

Second Advisor

Krish Judd

Third Advisor

Marianne Laporte

Abstract

Vitamin C Defective l (VTC I) is the major pyrophosphorylase involved in guanosine diphosphomannose (GDP-mannose) biosynthesis in the plantArabidopsis thaliana and it catalyzes the conversion of mannose I-phosphate and guanosine triphosphate (GTP) to GDP-mannose and pyrophosphate (PPi). The GDP-mannose pyrophosphorylase (GMPPase) activity of VTCI is enhanced by the proteins KONJACI (KJCI) and KONJAC2 (KJC2), which are homologs ofVTCl. The purpose of this study was to analyze the effect of the KJC proteins on the GDP-glucose pyrophosphorylase (GGPPase) activity of VTCl. We hypothesized that the GGPPase activity of VTCl may also be enhanced due to interactions with KJCI and/or KJC2 due to the structural similarities between mannose I-phosphate and glucose I-phosphate. Enzyme assays were conducted to analyze the GMPPase and GGPPase activity of VTCl. We found that while in vitro assays indicated that VTC I was able to catalyze both GMPP and GGPP reactions, they did not conclusively demonstrate the effect of the KJC proteins on the GMPPase and GGPPase activity of VTCl. Replicates of the assays will need to be conducted to conclude whether or not the KJC proteins enhance the GGPPase activity of VTCI.

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