UNT Theses and Dissertations - 17 Matching Results

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O-Acetylserine Sulhydralase-A from Salmonella typhimurium LT-2: Thermodynamic Properties and SPectral Identification of Intermediates

Description: O-Acetylserine Sulfhydrylase (OASS) is a pyridoxal phosphate enzyme that catalyzes the reaction of O-acetyl-Lserine with sulfide to give L-cysteine. OASS is present as two isoforms, designated -A and -B. The kinetic mechanism of OASS-A is well known and there is also much known concerning the acid-base chemistry of the enzyme. However, little is known concerning the location of the rate determining steps, the sequencing of chemical steps that occur at the active site, or the nature of the rate … more
Date: August 1993
Creator: Simmons, James Walter
Partner: UNT Libraries
open access

Analysis of a Human Transfer RNA Gene Cluster and Characterization of the Transcription Unit and Two Processed Pseudogenes of Chimpanzee Triosephosphate Isomerase

Description: An 18.5-kb human DNA segment was selected from a human XCharon-4A library by hybridization to mammalian valine tRNAiAc and found to encompass a cluster of three tRNA genes. Two valine tRNA genes with anticodons of AAC and CAC, encoding the major and minor cytoplasmic valine tRNA isoacceptors, respectively, and a lysine tRNAcuu gene were identified by Southern blot hybridization and DNA sequence analysis of a 7.1-kb region of the human DNA insert. At least nine Alu family members were found inte… more
Date: August 1990
Creator: Craig, Leonard C. (Leonard Callaway)
Partner: UNT Libraries
open access

Application of Synthetic Peptides as Substrates for Reversible Phosphorylation

Description: Two highly homologous synthetic peptides MLC(3-13) (K-R-A-K-A-K-T-TK-K-R-G) and MLC(5-13) (A-K-A-K-T-T-K-K-R-G) corresponding to the amino terminal amino acid sequence of smooth muscle myosin light chain were utilized as substrates for protein kinase C purified from murine lymphosarcoma tumors to determine the role of the primary amino acid sequence of protein kinase C substrates in defining the lipid (phosphatidyl serine and diacylglycerol) requirements for the activation of the enzyme. Remova… more
Date: August 1992
Creator: Abukhalaf, Imad Kazem
Partner: UNT Libraries
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Autophosphorylation and Autoactivation of an S6/H4 Kinase Isolated From Human Placenta

Description: A number of protein kinases have been shown to undergo autophosphorylation, but few have demonstrated a coordinate increase or decrease in enzymatic activity as a result. Described here is a novel S6 kinase isolated from human placenta which autoactivates through autophosphorylation in vitro. This S6/H4 kinase, purified in an inactive state, was shown to be a protein of Mr of 60,000 as estimated by SDS-PAGE and could catalyze the phosphorylation of the synthetic peptide S6-21, the histone H4, a… more
Date: May 1994
Creator: Dennis, Patrick B. (Patrick Brian)
Partner: UNT Libraries
open access

Characterization of a Human 28S Ribosomal RNA Retropseudogene and Other Repetitive DNA Sequence Elements Isolated from a Human X Chromosome-Specific Library

Description: Three genomic clones encompassing human DNA segments (designated LhX-3, LhX-4, and LhX5) were isolated from an X chromosome-specific library and subjected to analysis by physical mapping and DNA sequencing. It was found that these three clones are very rich in repetitive DNA sequence elements and retropseudogenes.
Date: May 1994
Creator: Wang, Suyue
Partner: UNT Libraries
open access

Cottonseed Microsomal N-Acylphosphatidylethanolamine Synthase: Identification, Purification and Biochemical Characterization of a Unique Acyltransferase

Description: N-Acylphosphatidylethanoiamine (NAPE) is synthesized in the microsomes of cotton seedlings by a mechanism that is possibly unique to plants, the ATP-, Ca2+-, and CoA-independent acylation ofphosphatidylethanolamine (PE) with unesterified free fatty acids (FFAs), catalyzed by NAPE synthase. A photoreactive free fatty acid analogue, 12-[(4- azidosalicyl)amino]dodecanoic acid (ASD), and its 125I-labeled derivative acted as substrates for the NAPE synthase enzyme.
Date: December 1998
Creator: McAndrew, Rosemary S. (Rosemary Smith)
Partner: UNT Libraries
open access

Dependence of the Kinetic Mechanism of Adenosine 3',5'-Monophosphate Dependent Protein Kinase Catalytic Subunit in the Direction of Magnesium Adenosine 5'-Diphosphate Phosphorylation on pH and the Concentration of Free Magnesium Ions

Description: To define the overall kinetic and chemical mechanism of adenosine 3',5'-monophosphate dependent protein kinase catalytic subunit, the mechanism in the direction of MgADP phosphorylation was determined, using studies of initial velocity in the absence and presence of dead-end inhibitors. The kinetic mechanism was determined as a function of uncomplexed Mg^2+ (Mg_f) at pH 7.2 and as a function of pH at low (0.5 mM) Mg_f. At pH 7.2 data are consistent with a random kinetic mechanism in the directi… more
Date: December 1992
Creator: Qamar, Raheel
Partner: UNT Libraries
open access

Fumarate Activation and Kinetic Solvent Isotope Effects as Probes of the NAD-Malic Enzyme Reaction

Description: The kinetic mechanism of activation of the NAD-malic enzyme by fumarate and the transition state structure for the oxidation malate for the NAD-malic enzyme reaction have been studied. Fumarate exerts its activating effect by decreasing the off-rate for malate from the E:Mg:malate and E:Mg:NAD:malate complexes. The activation by fumarate results in a decrease in K_imalate and an increase in V/K_malate by about 2-fold, while the maximum velocity remains constant. A discrimination exists between … more
Date: December 1992
Creator: Lai, Chung-Jeng
Partner: UNT Libraries
open access

Identification of Endogenous Substrates for ADP-Ribosylation in Rat Liver

Description: Bacterial toxins have been shown to modify animal cell proteins in vivo with ADPR. Animal cells also contain endogenous enzymes that can modify proteins. Indirect evidence for the existence in vivo of rat liver proteins modified by ADPR on arginine residues has been reported previously. Presented here is direct evidence for the existence of ADP-ribosylarginine in rat liver proteins. Proteins were subjected to exhaustive protease digestion and ADP-ribosyl amino acids were isolated by boronate ch… more
Date: May 1992
Creator: Loflin, Paul T. (Paul Tracey)
Partner: UNT Libraries
open access

Induced CSF-1 Production and its Effects on C-FMS Transfected Monoblastic U937 Cells

Description: This study examined how the monoblast-like human histiocytic lymphoma cell line U937 can be induced by phorbol 12-myristrate 13-acetate (PMA) to undergo differentiation. In order to study the mechanism of action of CSF-1, a CSF-1 receptor gene (c-fms) was transfected into U937 cells. Exogenous CSF-1 treatment induced an autocrine response in this CSF-1 was determined and all events were shown to be time dependent. CSF-1 stimulation also enhanced proto-oncogene c-jun and c-myc gene expression. … more
Date: August 1992
Creator: Liu, Mu-ya
Partner: UNT Libraries
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Kinetic and Chemical Mechanism of 6-phosphogluconate Dehydrogenase from Candida Utilis

Description: A complete initial velocity study of the 6-phosphogluconate dehydrogenase from Candida utilis in both reaction directions suggests a rapid equilibrium random kinetic mechanism with dead-end E:NADP:(ribulose 5-phosphate) and E:NADPH:(6- phosphogluconate) complexes. Initial velocity studies obtained as a function of pH and using NAD as the dinucleotide substrate for the reaction suggest that the 2'-phosphate is critical for productive binding of the dinucleotide substrate. Primary deuterium isoto… more
Date: May 1993
Creator: Berdis, Anthony J. (Anthony Joseph)
Partner: UNT Libraries
open access

Kinetic and Chemical Mechanism of O-Acetylserine Sulfhydrylase-B from Salmonella Typhimurium

Description: Initial velocity studies of O-acetylserine sulfhydrylase-B (OASS-B) from Salmonella typhimurium using both natural and alternative substrates suggest a Bi Bi ping pong kinetic mechanism with double substrate competitive inhibition. The ping pong mechanism is corroborated by a qualitative and quantitative analysis of product and dead-end inhibition. Product inhibition by acetate is S-parabolic noncompetitive, indication of a combination of acetate with E followed by OAS. These data suggest some … more
Date: August 1993
Creator: Tai, Chia-Hui
Partner: UNT Libraries
open access

Modification of Cardiac Membrane Gsα by an Endogenous Arginine-Specific Mono-Adp-Ribosyltransferase

Description: The mechanism by which nicotinamide adenine dinucleotide (NAD) stimulates the activity of adenylate cyclase (AC) in canine plasma membrane has been studied. Using [3 2P]-NAD, the activation by NAD was correlated with the radiolabeling of the stimulatory guanosine triphosphate (GTP) binding protein Gsa. Further characterization demonstrated that the modification occurred only in the presence of G-protein activators and that arginine residue(s) were modified by ADP-ribose by the action of a mono-… more
Date: December 1993
Creator: Coyle, Donna L. (Donna Lynn)
Partner: UNT Libraries
open access

Nucleotide Inhibition of Glyoxalase II

Description: The glyoxalase system mediates the conversion of methylglyoxal, a toxic ketoaldehyde, to D-lactic acid. The system is composed of two enzymes, glyoxalase I (Glo-I) and glyoxalase II (Glo-II), and exhibits an absolute requirement for a catalytic quantity of glutathione (GSH). Glo-I catalyzes the isomerization of a hemithioacetal, formed non-enzymatically from methylglyoxal and GSH, to the corresponding a -D-hydroxyacid thioester, s-D-lactoylglutathione (SLG). Glo-II catalyzes the irreversible br… more
Date: May 1999
Creator: Gillis, Glen S
Partner: UNT Libraries
open access

Preparation and Characterization of Model Conjugates for the Study of Proteins Modified by ADP-ribose

Description: Modification of proteins by ADP-ribose has been shown to be a versatile modification with respect to the amino acid side chain. The results described here will allow the study of the biological importance of ADP-ribose glycation and also allow differentiation on crude extracts between enzymatic modifications from protein ADP-ribose glycation that can occur due to the presence of NAD glycohydrolases.
Date: August 1992
Creator: Cervantes-Laurean, Daniel
Partner: UNT Libraries
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