The kinetic relationship between the activities of multifunctional enzymes from folate-mediated one-carbon metabolism were examined. Formyltetrahydrofolate dehydrogenase catalyzes the main disposal reaction for excess one-carbon units produced in the liver. The enzyme, which catalyzes also a hydrolytic reaction, was purified from porcine liver and a radioactive assay was developed to measure both activities simultaneously. These and other kinetic measurements established that the dehydrogenase and hydrolase are kinetically independent activities of a single type of polypeptide. NAD-dependent methylenetetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase is found in all transformed mammalian cells and catalyzes sequential reactions with channeling of the metabolic intermediate. However, these activities are kinetically independent in contrast to similar activities of the NADP-dependent trifunctional enzyme found in all eukaryotic cells. These properties explain the observation that only the NAD-dependent enzyme conjugate can catalyze the conversion of formyl- to methylenetetrahydrofolate in vitro.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.75844 |
| Date | January 1988 |
| Creators | Rios-Orlandi, Ethel Marie |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biochemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000723507, proquestno: AAINL48530, Theses scanned by UMI/ProQuest. |
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