Departamento de Botánica, Ecología y Fisiología Vegetal, Grupo de Fisiología Molecular y Biotecnología de Plantas, Campus Rabanales, Edif, Severo Ochoa, 1(a) Planta, Universidad de Córdoba, 14071-Córdoba, Spain.
Plant Physiol Biochem. 2012 Apr;53:54-60. doi: 10.1016/j.plaphy.2012.01.012. Epub 2012 Jan 26.
Common bean (Phaseolus vulgaris) seedlings accumulate ureides derived from purines after germination. The first step in the conversion of purines to ureides is the removal of the 5'-phosphate group by a phosphatase that has not been established yet. Two main phosphatase activities were detected in the embryonic axes of common bean using inosine monophosphate as substrate in an in-gel assay. Both activities differed in their sensitive to the common phosphatase inhibitor molybdate, with the molybdate-resistant as the first enzyme induced after radicle protrusion. The molybdate-resistant phosphatase has been purified to electrophoretic homogeneity and this is the first enzyme which shows this resistance purified and characterized from plant tissues. The native enzyme was a monomer of 55 kDa and it showed highest activity with nucleotides as substrates, with the K(m) values in the micromolar range. Among nucleotides, the highest specific constant (V(max)/K(m)) was observed for adenosine monophosphate. Furthermore, the enzyme was inhibited by nucleosides, the products of the enzymatic reaction, with maximum effect for adenosine. Common bean seedlings imbibed in the presence of adenosine monophosphate in vivo showed the highest molybdate-resistant phosphatase activity in the axes in addition to increased ureide content. The data presented suggests that purified phosphatase is involved in nucleotide metabolism in embryonic axes from common bean.
菜豆幼苗在萌发后会积累来自嘌呤的尿囊素。嘌呤转化为尿囊素的第一步是通过一种尚未确定的磷酸酶去除 5'-磷酸基团。在菜豆胚轴中使用肌苷单磷酸作为底物的凝胶内测定法检测到两种主要的磷酸酶活性。这两种活性对常见的磷酸酶抑制剂钼酸盐的敏感程度不同，钼酸盐抗性酶是在胚根伸出后诱导的第一种酶。钼酸盐抗性磷酸酶已被纯化至电泳纯，这是从植物组织中纯化和表征的第一种表现出这种抗性的酶。天然酶是一种 55 kDa 的单体，它以核苷酸为底物表现出最高的活性，其 K(m) 值在微摩尔范围内。在核苷酸中，对单磷酸腺苷的特异性常数 (V(max)/K(m)) 最高。此外，该酶被酶促反应的产物核苷抑制，其中对腺苷的抑制作用最大。在体内用腺苷单磷酸浸泡的菜豆幼苗，除了尿囊素含量增加外，在胚轴中表现出最高的钼酸盐抗性磷酸酶活性。所提供的数据表明，纯化的磷酸酶参与了菜豆胚轴中的核苷酸代谢。
