The purpose of this research was to characterize the Escherichia coli, E. coli, allantoinase enzyme. Allantoinase catalyses the conversion allantoin to allantoate via the hydrolysis of a cyclic amide bond and is coded for by the allB gene. The enzyme is a member of the amidohydrolase superfamily. Amidohydrolase superfamily enzymes have a common (αβ)8-barrel structure but catalyze the hydrolysis of many different substrates by a common mechanism. The structural characteristics and roles of divalent cations of enzymes in this superfamily will be discussed and related to previous work conducted on allantoinases. In this work, the metal dependence of allantoinase was initially studied by Mn, Co, Zn, Cd, and Ni-supplemented assays of enzyme of very low metal content. By changing the growth conditions under which the allB was overexpressed in E. coli, and the addition of Zn, Co or Mn to the culture, enzyme with bound Zn (ZnALN), Co (CoALN) or Mn (MnALN) was produced. The pH dependence of log (kcat/KM) for allantoinase in the presence of MnCl2, ZnALN and CoALN followed a bell-shaped curve, indicating that one ionizable group needed to be deprotonated and the deprotonation of a second group caused a decrease in catalytic activity. The pK1 for ionization at low pH was dependent upon which divalent cation was present and is concluded to be that of the deprotonation of water. A structural model of allantoinase with bound allantoin was constructed and used to determine which amino acid residues may be involved in catalysis. Allantoinase mutants R67K, C152A, C152S, C287A, C287S, S317A, D315N and W332F were purified. The kinetic parameters kcat, KM and kcat/KM of wild type and mutant allantoinases were compared. The possible roles of these amino acid residues in catalysis and substrate binding, and the results of the pH rate profiles are discussed. A catalytic mechanism for allantoinase is proposed.

Con el objetivo de determinar los serotipos más frecuente de Escherichia coli Enteropatógena (EPEC) en los cuadros diarreicos agudos de niños menores de cinco años, se diseñó una investigación de tipo descriptivo, transversal, y observacional. La población de estudio estuvo constituida por 251 niños tratados en forma ambulatoria en el Hospital Nacional Docente Madre Niño “San Bartolomé” durante los meses de noviembre del 2000 a marzo del 2001. Se encontró 42 % (105 casos) de coprocultivos positivos a bacterias enteropatógenas, siendo Escherichia coli enteropatógena (EPEC) con 29,2 % (35 casos), la segunda causa más frecuente después de Shigella sp. Los serotipos de EPEC encontrados fueron: 9 casos del O119, 8 casos de O26, 6 casos del O55 y 2 casos del O86. Se concluye que lo serotipos más frecuentes de EPEC en los cuadros diarreicos agudos de niños menores de cinco años fueron el O119 y el O26.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 149-164). Available also in a digital version from Dissertation Abstracts.

Thèse doctorat : Ecologie Microbienne : Villeurbanne, INSA : 2005. / Titre provenant de l'écran-titre. Bibliogr. p. 107-121.

Reproduction de : Thèse de doctorat : Écologie microbienne : Lyon 1 : 2007. / Titre provenant de l'écran titre. 335 réf. bibliogr.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Hung-wen Liu. Vita. Includes bibliographical references. Also available from UMI.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: George Georgiou. Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--Miami University, Dept. of Microbiology, 2003. / Title from first page of PDF document. Document formatted into pages; contains vi, 94 p. : ill. Includes bibliographical references (p. 90-94).