Comparative aspects of aminooxyacetate inhibition of glycine oxidation and aminotransferase activity of pea leaf mitochondria |
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| Affiliation: | 1. Department of Chemistry, University of Otago, Dunedin, New Zealand;2. GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany;3. Riddet Institute, Department of Human Nutrition, University of Otago, Dunedin, New Zealand;4. Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, UK;1. Department of Pathology, Hospital de la Santa Creu i Sant Pau. Institute of Biomedical Research (IIB Sant Pau). Autonomous University of Barcelona, 08041 Barcelona, Spain;2. Department of Immunology, Hospital de la Santa Creu i Sant Pau. Institute of Biomedical Research (IIB Sant Pau), 08041 Barcelona, Spain;3. Department of Gynaecology and Obstetrics, Hospital de la Santa Creu i Sant Pau, 08041 Barcelona, Spain;1. Institute of Infectious Diseases and Molecular Medicine, Division of Medical Virology, University of Cape Town, South Africa;2. National Institute for Communicable Diseases of the National Health Laboratory Services, South Africa;3. National Health Laboratory Service, Cape Town, South Africa |
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| Abstract: | Aminooxyacetate (AOA) was found to inhibit glycine oxidation by pea leaf mitochondria at micromolar levels. The inhibition resulted from an inhibition of both glycine decarboxylase and serine hydroxymethyltransferase (SHMT) activity. Aspartate: 2-oxoglutarate aminotransferase (AsAT) and alanine: 2-oxoglutarate aminotransferase activities of pea leaf mitochondria were also very sensitive to AOA inhibition. Inhibition of both glycine oxidation and aminotransferase activity was likely competitive with respect to the amino group substrate, but also displayed a time-dependent increase in inhibition at constant AOA concentration. In the case of glycine oxidation, this time-dependent component may be related to the rate of penetration of AOA across the inner mitochondrial membrane. Furthermore, the AOA-inhibition of glycine oxidation could be reversed by pyridoxal 5-phosphate (PLP), whereas AOA-inhibited aminotransferase activity was not reversed. The results indicate that the pyridoxal 5-phosphate antagonist, AOA, results in varying types of inhibition depending on the type of enzyme involved. |
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