{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/86755"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/86755","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"A Characterization of Aspartyl Peptidases in Salmonella Typhimurium","abstract":"Few of the peptidases previously characterized from Salmonella typhimurium are capable of hydrolyzing aspartyl peptides. Peptidase E, an aspartyl specific dipeptidase, was the first member of a new family of peptide hydrolases that now includes peptidases from other proteobacteria and from two eukaryotes. It is shown that Peptidase E from Xenopus laevis has the same substrate specificity as Peptidase E from S. typhimurium, indicating that in this family of enzymes both the catalytic and the substrate specificity have been conserved. An alignment of the amino acid sequences of the Peptidase E family allowed for potentially important residues to be identified. Through site-directed mutagenesis of the S. typhimurium pepE, it was proposed that this enzyme is a serine hydrolase that utilizes a catalytic triad of serine, aspartate, and histidine. In extracts of a pepE strain, two additional Asp-X hydrolases were detected. The identity of each of these enzymes as well as evidence of a third Asp-X hydrolase are presented in this thesis. Two of these enzymes are shown most rapidly hydrolyze isoaspartyl peptides (also called beta-aspartyl peptides). Of the two isoaspartyl peptidases, one is a homolog of IadA from E. coli and the other is described for the first time in this work and is encoded by a previously unknown open reading frame called ybiK in E. coli. The ybiK gene product is a threonine hydrolase that is a member of the Ntn (N-terminal nucleophile) family of enzymes. It is synthesized as a 32 kD polypeptide that dimerizes and undergoes processing, presumably autocatalytic, into an active form, which is a 60 kD heterotetramer. A strain of S. typhimurium lacking all of the broad specificity peptidases, as well as the aspartyl peptidases described here is still capable of growth on Asp-Leu as a leucine source. This growth is attributed to the remaining peptidase. This peptidase is specific for alpha-aspartyl peptides, has a native molecular mass of 70 kD, and has the unusual property of requiring manganese for activity.","abstract_html":"Few of the peptidases previously characterized from Salmonella typhimurium are capable of hydrolyzing aspartyl peptides. Peptidase E, an aspartyl specific dipeptidase, was the first member of a new family of peptide hydrolases that now includes peptidases from other proteobacteria and from two eukaryotes. It is shown that Peptidase E from Xenopus laevis has the same substrate specificity as Peptidase E from S. typhimurium, indicating that in this family of enzymes both the catalytic and the substrate specificity have been conserved. An alignment of the amino acid sequences of the Peptidase E family allowed for potentially important residues to be identified. Through site-directed mutagenesis of the S. typhimurium pepE, it was proposed that this enzyme is a serine hydrolase that utilizes a catalytic triad of serine, aspartate, and histidine. In extracts of a pepE strain, two additional Asp-X hydrolases were detected. The identity of each of these enzymes as well as evidence of a third Asp-X hydrolase are presented in this thesis. Two of these enzymes are shown most rapidly hydrolyze isoaspartyl peptides (also called beta-aspartyl peptides). Of the two isoaspartyl peptidases, one is a homolog of IadA from E. coli and the other is described for the first time in this work and is encoded by a previously unknown open reading frame called ybiK in E. coli. The ybiK gene product is a threonine hydrolase that is a member of the Ntn (N-terminal nucleophile) family of enzymes. It is synthesized as a 32 kD polypeptide that dimerizes and undergoes processing, presumably autocatalytic, into an active form, which is a 60 kD heterotetramer. A strain of S. typhimurium lacking all of the broad specificity peptidases, as well as the aspartyl peptidases described here is still capable of growth on Asp-Leu as a leucine source. This growth is attributed to the remaining peptidase. This peptidase is specific for alpha-aspartyl peptides, has a native molecular mass of 70 kD, and has the unusual property of requiring manganese for activity.","abstract_has_math":false,"creators":["Lassy, Rachel Anne Larsen"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Microbiology","degree_department":null,"school":null,"contributors":["Miller, Charles G."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-28T15:17:51Z","date_published":"2015-09-28T15:17:51Z","updated_at":"2026-07-22T22:26:27Z","subjects":["Chemistry, Biochemistry"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI9955640"],"render_values":[{"text":"(MiAaPQ)AAI9955640","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/86755","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Miller, Charles G."]},{"key":"dc:creator","label":"Author","values":["Lassy, Rachel Anne Larsen"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-28T15:17:51Z","10000-01-01","2000"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Microbiology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry, Biochemistry"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/86755","(MiAaPQ)AAI9955640"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Few of the peptidases previously characterized from Salmonella typhimurium are capable of hydrolyzing aspartyl peptides. Peptidase E, an aspartyl specific dipeptidase, was the first member of a new family of peptide hydrolases that now includes peptidases from other proteobacteria and from two eukaryotes. It is shown that Peptidase E from Xenopus laevis has the same substrate specificity as Peptidase E from S. typhimurium, indicating that in this family of enzymes both the catalytic and the substrate specificity have been conserved. An alignment of the amino acid sequences of the Peptidase E family allowed for potentially important residues to be identified. Through site-directed mutagenesis of the S. typhimurium pepE, it was proposed that this enzyme is a serine hydrolase that utilizes a catalytic triad of serine, aspartate, and histidine. In extracts of a pepE strain, two additional Asp-X hydrolases were detected. The identity of each of these enzymes as well as evidence of a third Asp-X hydrolase are presented in this thesis. Two of these enzymes are shown most rapidly hydrolyze isoaspartyl peptides (also called beta-aspartyl peptides). Of the two isoaspartyl peptidases, one is a homolog of IadA from E. coli and the other is described for the first time in this work and is encoded by a previously unknown open reading frame called ybiK in E. coli. The ybiK gene product is a threonine hydrolase that is a member of the Ntn (N-terminal nucleophile) family of enzymes. It is synthesized as a 32 kD polypeptide that dimerizes and undergoes processing, presumably autocatalytic, into an active form, which is a 60 kD heterotetramer. A strain of S. typhimurium lacking all of the broad specificity peptidases, as well as the aspartyl peptidases described here is still capable of growth on Asp-Leu as a leucine source. This growth is attributed to the remaining peptidase. This peptidase is specific for alpha-aspartyl peptides, has a native molecular mass of 70 kD, and has the unusual property of requiring manganese for activity.","Made available in DSpace on 2015-09-28T15:17:51Z (GMT). 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Peptidase E, an aspartyl specific dipeptidase, was the first member of a new family of peptide hydrolases that now includes peptidases from other proteobacteria and from two eukaryotes. It is shown that Peptidase E from Xenopus laevis has the same substrate specificity as Peptidase E from S. typhimurium, indicating that in this family of enzymes both the catalytic and the substrate specificity have been conserved. An alignment of the amino acid sequences of the Peptidase E family allowed for potentially important residues to be identified. Through site-directed mutagenesis of the S. typhimurium pepE, it was proposed that this enzyme is a serine hydrolase that utilizes a catalytic triad of serine, aspartate, and histidine. In extracts of a pepE strain, two additional Asp-X hydrolases were detected. The identity of each of these enzymes as well as evidence of a third Asp-X hydrolase are presented in this thesis. Two of these enzymes are shown most rapidly hydrolyze isoaspartyl peptides (also called beta-aspartyl peptides). Of the two isoaspartyl peptidases, one is a homolog of IadA from E. coli and the other is described for the first time in this work and is encoded by a previously unknown open reading frame called ybiK in E. coli. The ybiK gene product is a threonine hydrolase that is a member of the Ntn (N-terminal nucleophile) family of enzymes. It is synthesized as a 32 kD polypeptide that dimerizes and undergoes processing, presumably autocatalytic, into an active form, which is a 60 kD heterotetramer. A strain of S. typhimurium lacking all of the broad specificity peptidases, as well as the aspartyl peptidases described here is still capable of growth on Asp-Leu as a leucine source. This growth is attributed to the remaining peptidase. 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