FIGURE 2.

Actions of guanylate kinase on nucleoside monophosphates containing normal and oxidized guanine bases. A, the action of GMK on GMP. The reaction mixture (20 μl) contained 0.2 mm GMP, 0.2 mm ATP, 50 mm Hepes (pH 7.4), 4 mm MgCl₂, 40 mm (NH₄)₂SO₄, and 20 ng of a purified preparation of GMK. The reaction was carried out at 37 °C for 8 min, and then samples were applied to HPLC using a TSKgel DEAE-2 SW column (Tosoh, Tokyo, Japan). B, the action of GMK on 8-oxo-GMP. The reaction was performed as described above except that 8-oxo-GMP was treated with 1 μg of the GMK protein for 30 min. C, the time courses of reactions for GMP (●) and 8-oxo-GMP (○) with GMK. D, the time courses of reactions for dGMP (●) and 8-oxo-dGMP (○) with GMK. For C and D, the reactions were carried out with 20 ng of GMK preparation and 0.2 mm substrate nucleotides in 20 μl of a reaction mixture containing 50 mm Hepes (pH 7.4), 0.2 mm ATP, 4 mm MgCl₂, and 40 mm (NH₄)₂SO₄.