• Journal of Microbiology
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• v.44 no.1
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• pp.50-53
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• 2006

Cys-29 and Cys-251 of Streptomyces albus valine dehydrogenase(ValDH) were highly conserved in the corresponding region of $NAD(P)^+$-dependent amino acid dehydroganase sequences. To ascertain the functional role of these cysteine residues in S. albus ValDH, site-directed mutagenesis was performed to change each of the two residues to serine. Kinetic analyses of the enzymes mutated at Cys-29 and Cys-251 revealed that these residues are involved in catalysis. We also constructed mutant ValDH by substituting valine for leucine at 305 by site-directed mutagenesis. This residue was chosen, because it has been proposed to be important for substrate discrimination by phenylalanine dehydrogenase (PheDH) and leucine dehydrogenase (LeuDH). Kinetic analysis of the V305L mutant enzyme revealed that it is involved in the substrate binding site. However it displayed less activity than the wild type enzyme toward all aliphatic and aromatic amino acids tested.

• Microbiology and Biotechnology Letters
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• v.28 no.3
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• pp.152-155
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• 2000

Cultural Conditions for the Improvement in Gibberellic Acid Productivity by a Mutant of Gibberellafujikuroi ATCC 12616-Gibberella fujikuroi G-36 . Dh, Young-Jun. Department of Food and Biotechnolog}'r Dongshm Umversity, Naju 520-714, Korea - A mutant Gibberella jujih/roi G- 36 was selected by metagenesis of G/bberella fitjikuroi ATCC 12616 with mutagens such as N-methy1-N'~nitro~N"nitrosoguanidine and hydroxylamine for improving productivity of gibberellic acid. The mutant strain produced gibberellic acid (70 mg/l) more than that of wilde type. A fermentation medium containing glucose, $NH_4N0_3$, $MgS0_4$, $KH_2P0_4$ and trace elements was deve]oped for the maximal production of a gibberellic acid by the mutanL The Guctuating cultural temperature that was vaded from 300e to 20DC resulted in higher GA yield than that of fixed cu1tura] temperature at $28^{\circ}C$.