Biochemistry Commons^™

Biochemical And Kinetic Analysis Of Phosphofructokinase In The Eukaryotic Human Pathogen Entamoeba Histolytica, Jin Cho

All Dissertations

Entamoeba histolytica is a water- and food-borne intestinal parasite that causes amoebiasis and liver abscess in ~100 million people each year leading to ~100,000 deaths. This amitochondriate parasite lacks many metabolic pathways including the tricarboxylic acid cycle and oxidative phosphorylation, and cannot synthesize purines, pyrimidines, or most amino acids. As a result, E. histolytica is presumed to rely on its modified pyrophosphate (PP_i)-dependent glycolytic pathway for ATP production during growth on glucose. This pathway relies on a PP_i-dependent rather than ATP-dependent phosphofructokinase (PFK) and thus has a net production of three ATP per glucose. However, in …

Biochemical Analyses Of Udgx-A Crosslinking Uracil-Dna Glycosylase, Chuan Liang

All Dissertations

DNA base damage is common due to exposure to various endogenous and exogenous factors. To repair the base lesions, such as uracil from cytosine deamination, enzymes from the uracil-DNA glycosylase (UDG) superfamily are critical, which can recognize the damaged base and initiate the base excision repair (BER) pathway. There used to be six families of proteins identified in the UDG superfamily until a new member, UDGX, was found in Mycobacterium smegmatis, which is a unique DNA-crosslinking UDG. In this dissertation work, a series of biochemical analyses of the newly found UDGX are performed, including the analyses of structures, functions, …

Characterization Of The Effects Of The Pyrazolopyrimidine Inhibitor Grassofermata (Nav-2729) In The Eukaryotic Pathogen Trypanosoma Brucei, Kristina Marie Parman

All Dissertations

The protozoan pathogen, Trypanosoma brucei, is the causative agent of sleeping sickness in humans and nagana in livestock in sub-Saharan Africa. T. brucei cycles between tsetse fly and mammalian hosts, and it is adapted to survive in diverse host tissues. Variant Surface Glycoprotein (VSG) plays a key role in immune evasion in the mammalian host. The VSG membrane anchor requires two myristates, 14-carbon saturated fatty acids (FAs) that are scarce in the host. T. brucei can synthesize FAs de novo, but also readily takes up exogenous FAs, despite lacking homologs to fatty acid uptake proteins found in other …

Fatty Acids And Parasitism: Towards A Better Understanding Of Lipid Metabolism In Trypanosoma Brucei, Joshua Saliutama

All Dissertations

Trypanosoma brucei is an extracellular eukaryotic parasite that causes sleeping sickness in humans and cattle. As an extracellular parasite, T. brucei relies on the host’s nutrients to satisfy its growth requirements. The parasite is unusual because it does not uptake most of the host’s lipid species. Instead, T. brucei prefers to perform de novo synthesis of most lipid species. One of the lipid species that T. brucei can both uptake and synthesize is fatty acids. In my thesis work, I investigated the dynamics of fatty acid uptake, metabolism, and utilization of T. brucei. My work starts by determining the …

Methyltransferase, Glucose Adaptation, And Import Complex In Trypanosoma Brucei, Emily Knight

All Dissertations

Trypanosoma brucei is a kinetoplastid parasite responsible for human African trypanosomiasis (HAT) and nagana, a livestock wasting disease, which both endemic to sub-Saharan Africa. Unique to kinetoplastids are the specialized peroxisomes, named glycosomes, which compartmentalize the first several steps of glycolysis and gluconeogenesis, nucleotide sugar biosynthesis, and many other metabolic processes. Kinetoplastids are unique in that they have a single mitochondrion. In this work, I present the first study into SET domain proteins in any kinetoplastid parasites. We have characterized a predicted SET domain protein, TbSETD3, that localizes to the mitochondrion and a depletion of the protein results in growth …

New Dna Repair And Demethylation Functions In Uracil Dna Glycosylase Superfamily, Chenyan Chang

All Dissertations

Uracil-DNA glycosylase (UDG) superfamily, which consists of several groups of enzymes that recognize the damaged DNA bases and initiate the base excision repair (BER) pathway, is most important in dealing with DNA deamination and other base modifications. Thymine DNA glycosylase (TDG), which belongs to family 2 in the UDG superfamily, is able to specifically recognize and cleave the 5-methylcytosine (mC) oxidative derivatives including 5-formylcytosine (fC), 5-carboxylcytosine (caC), 5-hydromethyluracil (hmU) caused by active demethylation or DNA damage. My dissertation work is mainly focused on the fC and caC glycosylase activity within UDG superfamily. Chapter 1 is a general introduction to the …

Glycolytic Inhibitors As Leads For Drug Discovery In The Pathogenic Free-Living Amoebae, Jillian Milanes

All Dissertations

The free-living amoeba, Naegleria fowleri, can cause a rare yet usually lethal infection of the brain called primary amebic meningoencephalitis. Because of poor diagnostics and limited treatment options, the mortality rate associated with the disease is >97%. Due to our finding that glucose is critical for trophozoite growth in culture, we have been interested in exploiting amoebae glucose metabolism to identify new potential drug targets. We have characterized the first enzyme of the glycolytic pathway, glucokinase (Glck), from N. fowleri and two other pathogenic free-living amoeba, Acanthamoeba castellanii and Balamuthia mandrillaris. We have assessed their biochemical properties and …

Acetate Metabolism In The Fungal Pathogen Cryptococcus Neoformans, Oly Ahmed

All Dissertations

Cryptococcus neoformans is an environmental basidiomycetous fungus with a worldwide distribution and a wide range of habitats. Inhalation of the desiccated yeasts or spores of C. neoformans often leads to opportunistic pulmonary infections in immunocompromised individuals, and in severe cases causes lethal meningitis following hematogenous dissemination. During infection, depending on the tissue and disease state, the invading fungi experience a range of nutrient microenvironments within the host body. As a result, rapid metabolic adaptations geared towards efficient utilization of carbon sources alternative to glucose become one of the prime determinants of survival and growth for the pathogen. Incidentally, cryptococcal infection …

The Role Of Fatty Acid Metabolism In The Pathogenesis Of Trypanosoma Brucei, Nava Poudyal

All Dissertations

Trypanosoma brucei is the protozoan parasite that causes African Sleeping Sickness in humans and nagana, a wasting disease in cattle. T. brucei completes its life cycle in two hosts, mammals and the tsetse fly insect vector. Due to the geographical restriction of the tsetse fly, the disease is endemic in sub-Saharan Africa. Both the insect and mammalian forms of the parasite need fatty acids to anchor their surface proteins. We worked on three projects on fatty acid metabolism and its role in immune evasion strategies of T. brucei. First, we assessed the role of T. brucei surface proteins in …

Investigating The Biochemical Properties Of A Novel Mutation, A194v, In Human Rad51, Briana Vollbeer

All Theses

DNA double-strand breaks (DSB) are one of the most serious DNA lesions because improper repair of a DSB can lead to loss of heterozygosity, aneuploidy, and cancer. One of the primary pathways to repair DSBs is homologous recombination (HR). HR resects the DNA around the DSB and then uses homologous DNA as a template to restore the broken sequence. RAD51 has a vital function in this pathway by forming a nucleoprotein filament on a resected end of the DSB. The nucleoprotein filament searches for homology within the homologous DNA. Once homology is located, strand invasion followed by strand exchange occurs. …

Characterization Of The Wee1 Homologues And The Investigation Of Factors Promoting Cellular Enlargement In Cryptococcus Neoformans, Rodney J. Colón Reyes

All Dissertations

Cryptococcus neoformans is an opportunistic fungal pathogen, infecting mainly immunocompromised individuals. As the main cause of cryptococcosis, it is responsible for over 180,000 deaths every year. As an environmental yeast, it has unique adaptations that allow it to proliferate in the human host. Among these adaptations its capacity to transition to an extreme phenotype known as Titan cells is of special interest to researchers. With sizes above 10 um and able to reach 70 um or more in cell size. This size is accompanied with a large vacuole, larger polysaccharide capsule, and an increased resistance to fluconazole (FLC). FLC is …

An Investigation Into The Roles Of Aldose Reductase And Acetate Kinase In The Metabolism Of Entamoeba Histolytica, Matthew B. Angel

All Dissertations

Entamoeba histolytica is an amoebic parasite that infects an estimated 90 million people worldwide and causes approximately 100,000 deaths per year. As the causative agent of amoebic dysentery, this food- and water-borne pathogen represents a significant public health burden worldwide, particularly in areas with poor sanitation. While treatments for amoebiasis exist, they are often limited in their effectiveness. Thus, efforts to better understand the biology and physiology of this organism are vital to the development of novel treatments for this disease.

E. histolytica lacks the enzymes for many common metabolic pathways such as the citric acid cycle and oxidative phosphorylation …

Floating Treatment Wetlands For Brackish Waters: Plant Selection And Nutrient Uptake Potential., Andrea Landaverde

All Theses

Brackish water bodies in coastal regions provide critical ecosystem services that support human and environmental health. Anthropogenic activities such as agricultural and industrial activities, construction, urban settlements, and tourism contribute to increased inputs of nitrogen (N) and phosphorus (P) in brackish coastal ecosystems. Excess nutrients can lead to impaired water quality and affect marine organisms. Floating treatment wetlands (FTWs) are a vegetated-base technology used to remove contaminants from water column, that has been mainly studied and applied in freshwater systems. Application of FTWs in brackish systems requires further investigation, as high salinity in brackish waters could result in toxicity to …

Characterization Of A Potential Glucose Transporter In Trypanosoma Brucei, Matthew Morgan

All Theses

Trypanosoma brucei, the African trypanosome, is an organism heavily dependent on glucose for ATP production during the infectious stage of its life cycle. Here, we have explored the role of an uncharacterized protein designated “novel glucose transporter” (NGT) as a potential glucose transporter. Sequence analyses suggests that NGT shares similarities (either at the primary sequence level or structurally) with Trypanosome Hexose Transporters 1 (TbTHT1), and human GLUT3, both of which are membrane sugar transporters. NGT was localized by fluorescence microscopy to subcellular structures consistent with lysosomes. Silencing NGT expression with RNA interference in parasites resulted in a growth defect …

Tackling Adverse Environment—Molecular Mechanism Of Plant Stress Response And Biotechnology Tool Development, Ning Yuan

All Dissertations

Abiotic and biotic stresses such as drought, salt, nutrition starvation, and pathogen infection are major factors threatening our agricultural production. With the rapidly increasing population and limited arable land area, genetic engineering of crops for new products with more stable and higher yield than conventional cultivars under adverse environment provides a powerful new tool for use in developing novel GMOs (Genetically Modified Organisms) to feed the large population in the immediate future. To develop novel GMOs with enhanced performance under adverse conditions, we need first to understand molecular mechanisms underlying plant stress response. To better understand how signaling transduction pathway …

Phosphotransacetylase And Xylulose 5-Phosphate/Fructose 6-Phosphate Phosphoketolase: Two Eukaryotic Partners Of Acetate Kinase, Tonya Taylor

All Dissertations

Although acetate is a predominant metabolite produced by many eukaryotic microbes, far less attention has been given to acetate metabolism in eukaryotes than in bacteria and archaea. Acetate kinase (Ack), which catalyzes the reversible phosphorylation of acetate from ATP, is a key enzyme in bacterial acetate metabolism. Ack primarily partners with phosphotransacetylase (Pta), which catalyzes the generation of acetyl phosphate from acetyl-CoA, but can also partner with xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp), which produces acetyl phosphate from either xylulose 5-phosphate or fructose 6-phosphate. The Ack-Pta pathway, found primarily in bacteria, is also present in lower eukaryotes such as the green …

Development, Validation, And Application Of Analytical Methods For Characterizing Adsorbed Protein Orientation, Conformation, And Bioactivity, Aby Thyparambil

All Dissertations

The structure and bioactivity of adsorbed proteins are tightly interrelated and play a key role in their interaction with the surrounding environment. These factors are of critical importance in many biotechnological applications. However, because the bioactive state of an adsorbed protein is a function of the orientation, conformation, and accessibility of its bioactive site(s), the isolated determination of just one or two of these factors will typically not be sufficient to understand the structure-function relationships of the adsorbed layer. Rather a combination of methods is needed to address each of these factors in a synergistic manner to provide a complementary …

Allosteric Regulation Of Bacterial And Fungal Xylulose 5-Phosphate/ Fructose 6-Phosphate Phosphoketolases (Xfps), Katie Glenn

All Dissertations

Acetate is excreted as a metabolic end product in many microbes. Acetate production has primarily been studied in bacteria and archaea but is known to occur in eukaryotic organisms as well. For example, acetate is one of the most abundant metabolites excreted by the fungal pathogen Cryptococcus neoformans during cryptococcosis suggesting that acetate production may be important during pathogenesis. One possible pathway for acetate production in C. neoformans involves the enzymes xylulose 5-phosphate/ fructose 6-phosphate phosphoketolase (Xfp), which can generate acetyl phosphate from either fructose 6-phosphate (F6P) or xylulose 5-phosphate (X5P), and acetate kinase (Ack), which can then convert acetyl …

Development And Evaluation Of An Enrichment Culture For Reductive Dechlorination Of Tetrachloroethene Under Low Ph Conditions, Rui Xiao

All Theses

Perchloroethene (PCE) is a pollutant of major environmental concern at hazardous waste sites worldwide. PCE and trichloroethene (TCE) are suspected carcinogens and are ranked 16th and 31st, respectively, on the Environmental Protection Agency's priority list for hazardous substances, developed under the Comprehensive Environmental Response, Compensation, and Liability Act. As a consequence of the widespread use of chlorinated solvents (including PCE and TCE) for dry cleaning, chemical feedstocks, metal degreasing and other purposes, chloroethenes are widely distributed in the environment. Many soils and groundwater throughout the world are contaminated by chloroethenes. Therefore, further improvements are needed in clean-up methods. Bioaugmentation has …

Determination Of Pore Size Distribution In Capillary-Channeled Polymer (C-Cp) Fiber Stationary Phases By Inverse Size-Exclusion Chromatography (Isec) And The Study Of The Role Of Interstitial Fraction On C-Cp Fibers On Protein Binding Capacity, Zhengxin Wang

All Theses

ABSTRACT High performance liquid chromatography (HPLC), first used in the 1960's, is a rapidly evolving analytical technique, widely employed for identification, separation, and purification in biotechnology and pharmaceutical industries. The development of the stationary phases has played an important role in improving this technique. Each stationary phase will have its own disadvantages. Polysaccharide-based stationary phases such as cross-linked dextran cannot tolerate high pressures and linear velocities; silica stationary phases are rigid enough but slow mass transfer in the pores on the surface causes another problem; with the introduction of non-porous and small bead packing materials, the low surface area and …

Role Of Phosphoinositide-Based Signaling In Virulence In Entamoeba Histolytica, Amrita Koushik

All Dissertations

Entamoeba histolytica is an intestinal protozoan parasite and is the causative agent of amoebiasis. Upon entering the human host, cellular processes such as adhesion, phagocytosis, motility and secretion play a vital role in its propagation and pathogenicity. In other systems, each of these cellular processes is preceded by activation of signal transduction pathways, which often involve membrane phosphoinositides such as phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂). Little is known about phosphoinositide signaling in E. histolytica pathogenicity. In this study, we demonstrated that PI(4,5)P₂ is localized to cholesterol-rich microdomains, lipid rafts, of the E. histolytica membrane and to the trailing edge …

Regulation Of The Lipid Raft Localization Of The Gal/Galnac Lectin, An Adhesin On The Surface Of The Human Protozoan Parasite, Entamoeba Histolytica, Amanda Goldston

All Dissertations

Lipid rafts, sterol- and sphingolipid-rich membrane microdomains, have been shown to control virulence in a variety of parasites including Entamoeba histolytica, an intestinal parasite that causes dysentery and liver abscess. Parasite cell surface receptors, such as the Gal/GalNAc lectin, facilitate attachment to host cells and extracellular matrix. The Gal/GalNAc lectin binds to galactose or N-acetylgalactosamine residues on host components, and is composed of heavy (Hgl), intermediate (Igl), and light (Lgl) subunits. Although Igl is constitutively localized to lipid rafts, Hgl and Lgl transiently associate with this compartment in a cholesterol-dependent fashion. Exposure to bonafide Gal/GalNAc lectin ligands is associated with …

Lignin Modification In Arabidopsis And Populus For Studies Of Gene Function And Improving Lignin Degradation, Yi Xu

All Dissertations

Lignin is one of the most abundant biopolymers in plants and plays an important role in plant structure and stress defense. Lignin is also considered to be a hallmark of vascular plants because of its crucial role in plant terrestrialization. However, lignin is an undesired component in the pulp and paper industry, bioethanol production, and forage digestibility. Thus, understanding the functions and the evolution of lignin biosynthesis genes can not only advance our knowledge of the evolution of land-adaptation for vascular plants but also help guide the effort to exploit the potential for genetic manipulation of lignin for desirable traits …

An Investigation Of Trypanosoma Brucei Hexokinases: Localization, Oligomerization, And Inhibition, April Joice

All Dissertations

Trypanosoma brucei is the causative agent of African sleeping sickness in humans and nagana in livestock. The parasite inhabits multiple environmental niches including the bloodstream of the mammalian host and the mid-gut of the tsetse fly vector. While in the bloodstream of its mammalian host, the organism depends solely on glycolysis for production of ATP. My studies focus on the first enzyme in glycolysis, hexokinase.
T. brucei has two hexokinases, TbHK1 and TbHK2 that are 98.5% identical at the nucleotide level. The hexokinases are expressed in the glycosomes of both procyclic form and bloodstream form parasites. Glycosomes are peroxisome-like organelles …

Characterization Of De Novo Fatty Acid Biosynthesis In Soybean Somatic Embryo Plastids, Karen Clark

All Theses

A method for the isolation of intact physiologically active plastids from rapidly developing soybean (Glycine max L.) somatic embryos has been developed for the in vitro study of lipid metabolism. Using de novo fatty acid biosynthesis from 14C-acetate as a marker for physiological functionality, the greatest rates of fatty acid biosynthesis were recovered in 3000 x g fractions that were isolated in the presence of 0.5 M sorbitol, with essentially no activity occurring in the 3000 x g supernatant. Plastids purified on 10% Percoll were approximately 70 and 97 % free from mitochondrial and ER contamination, respectively, as judged …

Investigations Of The Ppi-Dependent Acetate Kinase From The Parasite Entamoeba Histolytica, Matthew Fowler

All Dissertations

Acetate, a short-chain fatty acid that plays a key role in all domains of life, can be utilized as a carbon source or excreted as a product of metabolism. Acetate kinase (ACK), a member of the acetate and sugar kinase-Hsp70-actin (ASKHA) enzyme superfamily, is responsible for the reversible phosphorylation of acetate to acetyl phosphate utilizing ATP as the phosphoryl donor. Acetate kinases are ubiquitous in the Bacteria, found in one genus of Archaea, and are also present in microbes of the Eukarya. A partially purified ACK which can utilize pyrophosphate (PP_i) as the phosphoryl donor in the acetyl …

Regulation Of Trypanosoma Brucei Hexokinase 1 And 2 On Multiple Levels: Transcript Abundance, Protein Expression And Enzyme Activity, Heidi Dodson

All Dissertations

Trypanosoma brucei, a unicellular eukaryotic parasite, is the causative agent of African sleeping sickness in sub-Saharan Africa. The parasite encounters two main environments as it progresses through its life cycle: the tsetse fly and the mammalian
bloodstream. Nutrient availability is distinct in the two environments, requiring the parasite to utilize diverse metabolic pathways to efficiently produce ATP for survival. Bloodstream form parasites (BSF), residing in a glucose rich environment, rely solely on
glycolysis for energy, while procyclic form (PF) parasites metabolize readily available proline and threonine in addition to glucose.
T. brucei expresses two hexokinases, the first enzyme in the …

Biomass V2.0: A New Tool For Bioprocess Simulation, Y Phan-Thien

All Theses

A simulation software (BioMASS - Biological Modeling and Simulation Software) was upgraded from the previous version and provided with additional enhancements. Several new bioprocess configurations and their subroutines have been added. The additional processes included continuous stirred tank reactor (CSTR) with biomass recycle, and CSTR with additional stream in the second stage. The primary goal in the development of BioMASS v2.0 was to provide users with a ready-to-use, expressive visual modeling tools. In this new version, output from simulation can be visualized in graphics. Printing, exporting, and saving file options also are available. In summary, BioMASS v2.0 offers an effective …

Understanding Gafp, A Plant Lectin With Broad Spectrum Inhibitory Activity, Alexis Nagel

All Dissertations

South Carolina and Georgia are the largest peach producing regions in the Southeastern United States, generating about $60 million worth (~90,000 tons) of fruit per year on average. Peaches and other stone-fruits (Prunus sp.) can be afflicted by a variety of root-associated diseases which negatively impact annual yield and long-term tree mortality. An engineered Prunus rootstock with enhanced resistance to soil-borne pathogens would therefore be of great benefit to the Southeastern peach industry. The Gastrodia anti-fungal protein (GAFP) is a monocot mannose-binding lectin which is able to inhibit the growth of multiple species of plant pathogenic fungi. Previous findings from …

Resistance And Dna Repair Mechanisms Under Nitrosative Stress In Mammalian And Microbial Systems, Hyun-Wook Lee

All Dissertations

Living organisms are exposed a nitrosative stress mediated by reactive nitrogen species (RNS) that can cause DNA damage and mutation. DNA base deamination is a typical damage occurred under nitrosative stress, which results in conversion of cytosine (C) to uracil (U), adenine (A) to hypoxanthine (I), and guanine (G) to xanthine (X) or oxanine (O). Base excision repair (BER) is an important pathway to remove deaminated DNA lesions in mammalian and microbial systems. My dissertation work concerns with genes and enzymes involved in resistance to nitrosative stress and DNA glycosylases in the BER pathway. In chapter one, I will briefly …