Studies on Metabolic Pathway of NAD in Yeast |
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Authors: | Shūzo Takei |
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Institution: | Tanaski Factory, Sankyō Co., Ltd., Tanashimachi 1450, Kitatama, Tokyo |
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Abstract: | The properties of yeast 5′-nucleotidase, one of NAD-metabolic system in yeast, were studied.1) The enzyme has optimum pH at 5.8~6.1 for its activity and is most stable at pH 6. It is inactivated completely at 55°C for 6 min, pH 7, but never at 40°C for 6 min. 2) The enzyme hydrolyzes only 5′-nucleotides of guanine, adenine, hypoxanthine, uracil and cytosine, but never splits nicotinamide mononucleotide, thiamine monophosphate, ribose 5-monophosphate and flavin mononucleotide. 3) The enzyme seems to have specially high affinity for 5′-AMP. 4) The enzyme activity is accelerated by addition of Co++ and Ni++, but inhibited by Ag+, Cu++, EDTA, I2 and N-bromosuccimide. Mg++, KCN, NaF and thiol reagents except p-chloromercuribenzoate have no effects. 5) Nucleosides have inhibitory effects, among which adenosine is most effective inhibitor. 6) The activity is reduced up to 30% by dialysis against 1 mm EDTA solution, and the reduced activity is completely reactivated by addition of Co++ or Ni++, but not by Mn++ or Mg++. |
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