The nonenzymic dephosphorylation of 5′-ribonucleotides (I) was investigated in buffer solutions ranging pH 1 to 12.5 at 100°C.
I was shown to be dephosphorylated in the pH 1 to 8 region being a maximum at around pH 4, but scarcely or not in alkaline media.
5′-Purine nucleotides such as 5′-inosinic acid (5′-IMP), 5′-guanylic acid (5′-GMP), and 5′-adenylic acid (5′-AMP) liberated more readily phosphoric acid in acidic media than 5′-pyrimidine nucleotides such as 5′-cytidylic acid (5′-CMP) and 5′-uridylic acid (5′-UMP).
2′ (3′) -Ribonucleotides (II), isomers of I, such as 2′ (3′) -GMP, 2′ (3′) -AMP, 2′ (3′) -CMP, and 2′ (3′) -UMP were dephosphorylated more rapidly in acidic media than I.
The rate constants of dephosphorylation of I and II at pH 5.0 at 100°C were in the following order,
2′ (3′) -GMP=2′ (3′) -AMP=2′ (3′) -CMP≥2′ (3′) -UMP>5′-GMP>5′-AMP≥5′-IMP>5′-UMP≥5′-CMP.
The dephosphorylation of I was found to be catalyzed greatly by Th (IV), Ce (III), Pb (II), and Au (III) and slightly by lanthanides (III). ZrO (II), Y (III), Ir (IV), and Cs (I), while inhibited by Al (III), Cr (III), UO
2 (II), In (III), Be (II), WO
4 (II), Nb (V), Sn (IV), and Sb
2O
7 (IV). On the other hand, many other metal ions were not effective in the dephosphorylation of I. Therefore, metal ions tested can be classified into three groups, that is, catalytic, inhibitory, and ineffective ions on the dephosphorylation of I.
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