食品中の核酸成分に関する研究 : (第8報)しいたけ子実体の核酸分解酵素系

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In a previous report (This Journal 43,344(1965)), it was assumed that the formation of 5'-GMP and other 5'-nucleotides during boiling process(mild heating with water)of Shii-take was due to the activities of the RNA- and nucleoside polyphosphate-degrading enzyme systems. A crude extract of Shii-take was saturated with (NH_4)_2SO_4,and the precipitate was fractionated by gradient elution with acetate buffer on the DEAE-cellulose column. Ribonuclease fractions thus obtained were designated as RNase A-1,A-2,and B.Both fractions A-1 and A-2 had an optimal temperature of 65℃ and a pH of 4.5,but in fraction B they were 65℃ and pH 8.0,respectively. Fractions D-1 and D-2 had a phosphodiesterase activity, decomposing bis-p-nitrophenylphosphate, with an optimal temperature of 60℃, and pH of 7.5. The optimal temperature and pH of phosphomonoesterase fraction (designated as PMase C) were 45℃ and pH 4.5,respectively, In the digests of yeast RNA by RNase A-1 in acetate buffer (pH 4.5) or by RNase B in Tris-buffer (pH 7.5), four kinds of 5'-nucleotides, namely, 5'-CMP, 5'-UMP, 5'-AMP, and 5'-CMP were accumulated abundantly. It is reasonab1e to consider that when Shii-take is heated in water (at temp.50-70℃, around pH 6.0), RNases A-1,A-2,and B in Shii-take hydrolyze RNA giving a mixture of four kinds of 5'-nucleotides. On the other hand, the activity of PMase C is low enough that PMase would have been inactivated at that temperature. Therefore, 5'-nucleotides furthermore formed are accumulated in a fairly large amount. It was suggested that when fresh Shii-take is incubated at pH 8.0,remarkable amounts of 5'-nucleotides are accumulated probably because of the degradation of RNA by RNase B, which are stable due to the lack of PMase C activity at that pH.
社団法人日本生物工学会の論文
1966-05-25

食品中の核酸成分に関する研究 : (第8報)しいたけ子実体の核酸分解酵素系

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