Hepatic tyrosine aminotransferase from the rainbow lizard Agama agama: purification and some properties |
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| Authors: | C O Echetebu F M Ifem Z O Echetebu |
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| Affiliation: | 1. Department of Pediatrics, Children''s Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA;2. Department of Neurology, Children''s Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA;3. Institute of Gerontology, Wayne State University, Detroit, MI, USA;4. Department of Anesthesiology, Hanyu General Hospital, Hanyu City, Saitama 348-8505, Japan;5. Trends in Cognitive Sciences, Cell Press, Cambridge, MA 02139, USA;1. Faculty of Electrical Engineering and Communication, Brno university of technology, Brno, Czech Republic;7. Faculty of Electrical Engineering and Communication, Brno university of technology, Brno, Czech Republic;71. Faculty of Electrical Engineering and Communication, Brno university of technology, Brno, Czech Republic;77. Faculty of Electrical Engineering and Communication, Brno university of technology, Brno, Czech Republic |
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| Abstract: | Tyrosine aminotransferase, induced by dexamethasone in the liver of the rainbow lizard, Agama agama, was extracted under optimal conditions which yield the native undegraded enzyme; purified by heat treatment at 65 degrees C, ammonium sulfate precipitation, chromatography on DEAE-Sephacel and Sephadex G-150-120 and then characterized. The enzyme was purified over 2000-fold to a specific activity of 2653 units/mg of protein. It had an optimum pH of 7.6 in potassium phosphate buffer, KmTyr: 1.0 mM; K alpha-KGm: 0.32 mM; Vmax: 1.33 nmol/min and a molecular weight of about 130,000. It was inhibited by L-glutamate (competitively, Ki, 2.5 mM), and by metal ions Ca2+, Mn2+, Zn2+, Hg2+ and Ag2+, but was unaffected by chelating agents and other divalent cations. Lizard hepatic cytosolic tyrosine aminotransferase was specific for L-tyrosine and alpha-ketoglutarate as substrates sensitive to sulfhydryl inactivation and to protection from thermal lability by alpha-ketoglutarate and pyridoxal phosphate. |
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