カツオ肝臓のNAD (P)加水分解酵素-II : NAD (P) nucleosidaseの物理化学的および酵素学的性質

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The physico-chomical and enzymatic properties of NAD (P) nucelsidase from skipjack liver was examined using a partially purified and two purified specimens (Frs. I and II). The molecular weights of Fr. I and II enzymes were estimated to be 30, 000 and 20, 000 and the isoelectric points to be 3.5 and 4.3, respectively. On SDS-electeophoresis, the Fr. II enzyme was found to be composed of two identical or similar subunits. PCMB titration in the presence and absence of 2-mercaptoenthanol demonstrated that this enzyme contains six sulfhydryl groups and two disulfide bonds per molecule. This skipjack enzyme showed a rather broad optimum pH ranging form 7.8 to 8.0. It was not activated by any of the divalent metal ions tested. On the contrary, a strong acid reversible inhibition was caused by ZnCl2 and CoCl2, Nicotinamide and isonicotinic acid hydrazide inhibited the enzyme uncompetitively, but adenine nucleoyides did not. The uncleosidase was found to hydrolyze NAD (P), 3-acetylridine adenine dinucleotide, and thioNAD, but it did not attack the reduced NAD (P)and nicotinamide mononuclecotide at all. This enzyme exhibited a strong transglycosidase activith.
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