Doctor of Philosophy, Miami University, 2011, Chemistry and Biochemistry

Although the glyoxalase system was discovered more than seven decades ago, its specific functional roles are still unclear. It is believed that the major role for this system is the chemical detoxification of methylglyoxal. However, the identification of isoforms that are non-catalytic with methylglyoxal and S-lactoylglutathione, a known substrate for the enzyme, has suggested that it may play additional roles. Also the observation of increased glyoxalase expression during stress conditions and diseased state, as well as the ability to introduce stress tolerance in plants by the over-expression of glyoxalase enzymes indicates that the system may be responsible for more than just methylglyoxal detoxification. The fact that the glyoxalase system is present across a range of species, and is expressed in almost all tissues highlights the significance of this system, and why it is an important topic to study. It is with this larger question that the research described herein was conducted. Specifically, the questions that this dissertation addresses are - what are the likely roles of two glyoxalase II-like enzymes (GLX2-1 and ETHE1) in Arabidopsis thaliana? To address this question we have used genetic, cellular, transcriptomic, and metabolomic tools to observe changes in the model plant Arabidopsis when expression levels of these genes are altered. The results of the study establish that GLX2-1 has a role in stress response in Arabidopsis thaliana, and that the absence of GLX2-1 increases the sensitivity of plants to stresses like anoxia (lack of oxygen) and high salt conditions. In case of ETHE1, our results suggest that perturbation of this gene causes pleiotropic effects on plant growth and survival, and possibly due to alterations in mitochondrial function.

Committee: Christopher A. Makaroff Dr. (Advisor); Michael W. Crowder Dr. (Committee Chair); Ann E. Hagerman Dr. (Committee Member); Carole Dabney Smith Dr. (Committee Member); Qingshun Quinn Li Dr. (Committee Member) Subjects: Biochemistry

Doctor of Philosophy, Miami University, 2008, Chemistry and Biochemistry

Mutations in the ETHE1 gene result in the complex metabolic disease ethylmalonic encephalopathy, which is characterized by symmetric brain lesions, lactic academia, elevated excretion of ethylmalonic acid, and death in the first decade of life. ETHE1-like genes are found in a wide range of organisms; however, to date, a detailed characterization of ETHE1 has not been performed. Therefore, neither the structure nor the function has been established for the enzyme in any organism. In this dissertation, a full structural characterization of the Arabidopsishomolog of ETHE1 as well as information on its functional role in plants is presented. We have obtained the first crystal structure of an ETHE1-like protein as well as performed metal and preliminary substrate analyses providing new insights into the possible role and substrate of ETHE1. In addition, we demonstrate that ETHE1 is essential for both plant growth and development.

Committee: Christopher Makaroff (Advisor) Subjects: