Title Kinetics of Intracellular Adenisine Deaminase to Substrate Analogs and Inhibitors in Aspergillus oryzae
Author Choi, Hye Seon
Address Department of Microbiology, Ulsan University
Bibliography Korean Journal of Microbiology, 32(1),84-90, 1994
Key Words adenosine deaminase, intracellular enzyme of Aspergillus oryzae, adenosine, 6-chloropurine riboside, 3'-deoxyadenosine, purine riboside, SH group
Abstract 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.
Download PDF Kor_320114_84-90p.pdf