Substitution of an arginyl residue for the active site lysyl residue (Lys258) of aspartate aminotransferase |
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| Authors: | S Kuramitsu Y Inoue S Tanase Y Morino H Kagamiyama |
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| Affiliation: | 1. Centro de Investigación en Alimentación y Desarrollo, A.C. Carretera a Ejido La Victoria Km. 0.6, Hermosillo, Sonora 83304, Mexico;2. Department of Chemistry, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA;3. El Colegio de Chihuahua, Calle Partido Díaz 4723 Esquina con Anillo Envolvente del PRONAF, Ciudad Juárez, Chihuahua 32310, Mexico |
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| Abstract: | The active site lysyl residue (Lys258) of E. coli aspartate amino transferase was substituted for an arginyl residue by oligonucleotide-directed, site-specific mutagenesis. The mutant enzyme was obviously unable to form an aldimine bond with pyridoxal 5'-phosphate but firmly bound the coenzyme. The finding that the mutation did not lead to entire loss in the enzymic activity suggests that Lys258 may not be essential but auxiliary for enzymic catalysis. It is also conceived that the positive charge provided by Arg258 may contribute to the enzymic catalysis. |
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