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KMID : 0364819940320010084
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Korean Journal of Microbiology
1994 Volume.32 No. 1 p.84 ~ p.90
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Kinetics of Intracellular Adenisine Deaminase to Substrate Analogs and Inhibitors in Aspergillus oryzae
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최혜선:Choi Hye-Seon
저자없음:No authors listed
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Abstract
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Kinetic parameters of various substrates and inhibitors were measured to elucidate the binding requirements of the active site of intracellular adenosine deaminase (ADA) in Aspergillus oryzae. 3’-Deoxyadenosine was the best substrate according to the value of relative kcat/K_m. Purine riboside was found to be the strongest inhibitor, suggesting the presence of ribose at N-9 of adenosine was crucial to binding. ADA also catalyzed the dechlorination of 6-chloropurine riboside, generating inosine and chloride ions. Substrate specificity of 6-chloropurine riboside was 0.86% of adenosine. Purine riboside, a competitive inhibitor of ADA, inhibit the dechlorination with similar K_I value, suggesting that the same binding site was involved in deamination and dechlorination. Among the sulfhydryl froup reagents, mercurials, p-chloromercuribenzoate(PCMB), mersalyl acid and HgCl_2 inactivated enzyme. Mersalyl acid-inactivated ADA was reactivated by thiol reagents, the inhibition constants and inhibition patterns were determined. Each inhibition was competitive with substrate. The K_I values of these mercurial reagents were lower in 10mM phosphate buffer than in 100mM phosphate buffer, showing phosphate dependency.
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KEYWORD
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adenosine deaminase, intracellular enzyme of Aspergillus oryzae, adenosine, 6-chloropurine riboside, 3´-deoxyadenosine, purine riboside, SH group
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