Chemical modification of intracellular cytosine deaminase fromChromobacterium violaceum YK 391 |
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Authors: | Jung Kim Tae Hyun Kim Tae Shick Yu |
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Affiliation: | (1) Department of Dental Hygiene, Suwon Women’s College, 441-748 Suwon, Korea;(2) Department of Ophthalmic Optics, Kyongbuk College of Science, 718-850 Kyungpook, Korea;(3) Department of Microbiology, Keimyung University, 704-701 Taegu, Korea |
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Abstract: | Cytosine deaminase (cytosine aminohydrolase, EC 3.5.4.1) stoichiometrically catalyzes the hydrolytic deamination of cytosine
and 5-fluorocytosine to uracil and 5-fluorouracil, respectively. Amino acid residues located in or near the active sites of
the intracellular cytosine deaminase fromChromobacterium violaceum YK 391 were identified by chemical modification studies. The enzymic activity was completely inhibited by chemical modifiers,
such as 1 mM NBS, chloramine-T, ρ-CMB, ρ-HMB and iodine, and was strongly inhibited by 1 mM PMSF and pyridoxal 5′-phosphate.
This chemical deactivation of the enzymic activity was reversed by a high concentration of cytosine. Furthermore, the deactivation
of the enzymic activity by ρ-CMB was also reversed by 1 mM cysteine-HCl, DTT and 2-mercaptoethanol. These results suggested
that cysteine, tryptophan and methionine residues might be located in or near the active sites of the enzyme, while serine
and lysine were indirectly involved in the enzymic activity. The intracellular cytosine deaminase fromC. violaceum YK 391 was assumed to be a thiol enzyme. |
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Keywords: | cytosine deaminase chemical modification Chromobacterium violaceum YK 391 intracellular cytosine deaminase |
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