{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/78799"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/78799","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Kinetic characterization of methyl donor substrates and inhibitors of human, pig, and rat liver betaine homocysteine S-methyltransferase (BHMT)","abstract":"This Thesis was approved for publication on 2015-05-01 at 08:42.","abstract_html":"This Thesis was approved for publication on 2015-05-01 at 08:42.","abstract_has_math":false,"creators":["Aubourg, Nadine"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Food Science & Human Nutrition","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-07-22T22:46:08Z","date_published":"2015-07-22T22:46:08Z","updated_at":"2026-07-22T22:26:12Z","subjects":["Homocysteine","Methionine","Betaine","Enzymology","Kinetic"],"languages":["en"],"rights":["Copyright 2015 Nadine Aubourg"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/78799","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Aubourg, Nadine"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-07-22T22:46:08Z","2017-07-23T09:15:27Z","2015-05","2015-05-01","2015-5"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Food Science & Human Nutrition"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"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":["Homocysteine","Methionine","Betaine","Enzymology","Kinetic"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2015 Nadine Aubourg"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/78799"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This Thesis was approved for publication on 2015-05-01 at 08:42.","Betaine-homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to homocysteine to form dimethylglycine and methionine, respectively. BMHT is primarily expressed in the liver and kidney of mammals. BHMT catalyzes an ordered bi bi reaction where the first product released, dimethylglycine, can compete for the betaine binding site and inhibit homocysteine utilization. There is considerable interest in the regulation of homocysteine metabolism since even moderate elevations in plasma total homocysteine have been established as an independent risk factor for the development of vascular diseases and thrombosis. In people with homocystinuria, treatment using supplemental betaine showed a significant decrease in total plasma homocysteine but does not lower homocysteine levels within the normal range, and the moderate levels that remain are highly correlated with vascular disease. Therefore, the BHMT catalyzed reaction is a target for the treatment of homocystinuria. Finding alternative methyl donors for the BHMT reaction that following methyl transfer have less potent inhibitory properties than dimethylglycine are desired. Sulfonium analogs of betaine are considered for this research. The main objectives of this research were to determine the inhibitory properties of the demethylated product of betaine and its sulfonium analogs and also to determine the Michaelis constants in order to use them as alternative methyl donors for the BHMT reaction in homocystinuric patients. The methyl donor substrates used are betaine, dimethylsulfonioacetate, dimethylsulfoniopropionate, and their respective demethylated products are dimethylglycine, methylthioacetate and methylpropionate. Dimethylglycine had the lowest IC50 values, ranging from 28 to 35 µM for all three enzymes. Methylthioacetate had IC50 values ranging from 65 to 106 µM, and values for methylthiopropionate ranged from 400 to 800 µM. There was no significant difference between the IC50 values obtained for the different enzymes when assayed in the presence of DMG or MTA, but for MTP the IC50 values were significantly different from one enzyme to another. Kinetic studies for betaine was conducted for all three enzymes. The Km of betaine varied from 1.8±0.5 mM, 0.7±0.06, and 0.5±0.06 mM for overexpressed human BHMT, pig and rat liver BHMT, respectively. We are unable to determine the Km for DMSA and DMSP. Further studies as the catalytic efficient (Kcat) for all three substrates are needed in other to determine which one could be a better alternative treatment for homocystinuria.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-05-01","The student, Nadine Aubourg, accepted the attached license on 2015-04-29 at 19:54.","The student, Nadine Aubourg, submitted this Thesis for approval on 2015-04-29 at 19:54.","DSpace SAF Submission Ingestion Package generated from Vireo submission #8201 on 2015-07-22 at 14:26:37","Made available in DSpace on 2015-07-22T22:46:08Z (GMT). No. of bitstreams: 2 AUBOURG-THESIS-2015.pdf: 895988 bytes, checksum: 47ead75a8ad2898735767d9f7dc4efb8 (MD5) LICENSE.txt: 4211 bytes, checksum: 8f6597dd03a7cd85e01ade1de8b900a1 (MD5) Previous issue date: 2015-05-01","Embargo set by: Seth Robbins for item 80040 Lift date: 2017-07-22T22:46:21Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 80040 on 2017-07-23T09:15:27Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Kinetic characterization of methyl donor substrates and inhibitors of human, pig, and rat liver betaine homocysteine S-methyltransferase (BHMT)"]}]}],"canonical_facts":{"dc:creator":["Aubourg, Nadine"],"dc:date":["2015-07-22T22:46:08Z","2017-07-23T09:15:27Z","2015-05","2015-05-01","2015-5"],"dc:description":["This Thesis was approved for publication on 2015-05-01 at 08:42.","Betaine-homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to homocysteine to form dimethylglycine and methionine, respectively. BMHT is primarily expressed in the liver and kidney of mammals. BHMT catalyzes an ordered bi bi reaction where the first product released, dimethylglycine, can compete for the betaine binding site and inhibit homocysteine utilization. There is considerable interest in the regulation of homocysteine metabolism since even moderate elevations in plasma total homocysteine have been established as an independent risk factor for the development of vascular diseases and thrombosis. In people with homocystinuria, treatment using supplemental betaine showed a significant decrease in total plasma homocysteine but does not lower homocysteine levels within the normal range, and the moderate levels that remain are highly correlated with vascular disease. Therefore, the BHMT catalyzed reaction is a target for the treatment of homocystinuria. Finding alternative methyl donors for the BHMT reaction that following methyl transfer have less potent inhibitory properties than dimethylglycine are desired. Sulfonium analogs of betaine are considered for this research. The main objectives of this research were to determine the inhibitory properties of the demethylated product of betaine and its sulfonium analogs and also to determine the Michaelis constants in order to use them as alternative methyl donors for the BHMT reaction in homocystinuric patients. The methyl donor substrates used are betaine, dimethylsulfonioacetate, dimethylsulfoniopropionate, and their respective demethylated products are dimethylglycine, methylthioacetate and methylpropionate. Dimethylglycine had the lowest IC50 values, ranging from 28 to 35 µM for all three enzymes. Methylthioacetate had IC50 values ranging from 65 to 106 µM, and values for methylthiopropionate ranged from 400 to 800 µM. There was no significant difference between the IC50 values obtained for the different enzymes when assayed in the presence of DMG or MTA, but for MTP the IC50 values were significantly different from one enzyme to another. Kinetic studies for betaine was conducted for all three enzymes. The Km of betaine varied from 1.8±0.5 mM, 0.7±0.06, and 0.5±0.06 mM for overexpressed human BHMT, pig and rat liver BHMT, respectively. We are unable to determine the Km for DMSA and DMSP. Further studies as the catalytic efficient (Kcat) for all three substrates are needed in other to determine which one could be a better alternative treatment for homocystinuria.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-05-01","The student, Nadine Aubourg, accepted the attached license on 2015-04-29 at 19:54.","The student, Nadine Aubourg, submitted this Thesis for approval on 2015-04-29 at 19:54.","DSpace SAF Submission Ingestion Package generated from Vireo submission #8201 on 2015-07-22 at 14:26:37","Made available in DSpace on 2015-07-22T22:46:08Z (GMT). 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