Abstract
1. Kinetic aspects of the reaction between crystalline bovine liver glutamate dehydrogenase and formiminoglutamate were investigated to establish the conditions under which the latter may interfere with the assay of glutamate by using glutamate dehydrogenase and to explain why formiminoglutamate accumulates in vivo after histidine loading, although it can react with glutamate dehydrogenase. The Km and Vmax. values were compared with those of the enzyme reacting with glutamate. At pH 7.4 Km for formiminoglutamate was much higher and Vmax. much lower than the values for glutamate. 2. The equilibrium constant at pH 7.0 was 0.017 micrometer with formiminoglutamate, i.e. about one two-hundredths that with glutamate. 3. In vivo the interaction between glutamate dehydrogenase and formiminoglutamate is minimal even when the concentration of the latter in the liver is greatly raised, as in cobalamine or folate deficiency after histidine loading. 4. At pH 9.3, i.e. under the conditions for the assay of glutamate by glutamate dehydrogenase, formiminoglutamate reacts readily with the enzyme.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Brosnan J. T., Krebs H. A., Williamson D. H. Effects of ischaemia on metabolite concentrations in rat liver. Biochem J. 1970 Mar;117(1):91–96. doi: 10.1042/bj1170091. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DIXON M. The determination of enzyme inhibitor constants. Biochem J. 1953 Aug;55(1):170–171. doi: 10.1042/bj0550170. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Engel P. C., Dalziel K. Kinetic studies of glutamate dehydrogenase. The reductive amination of 2-oxoglutarate. Biochem J. 1970 Jul;118(3):409–419. doi: 10.1042/bj1180409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Krebs H. A., Hems R., Tyler B. The regulation of folate and methionine metabolism. Biochem J. 1976 Aug 15;158(2):341–353. doi: 10.1042/bj1580341. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Williamson D. H., Lund P., Krebs H. A. The redox state of free nicotinamide-adenine dinucleotide in the cytoplasm and mitochondria of rat liver. Biochem J. 1967 May;103(2):514–527. doi: 10.1042/bj1030514. [DOI] [PMC free article] [PubMed] [Google Scholar]