玉米胚乳的磷酸化酶 I 和 II。
Phosphorylases I and II of Maize Endosperm.
机构信息
Department of Botany & Plant Pathology, Purdue University, Lafayette, Indiana 47907.
出版信息
Plant Physiol. 1968 Jan;43(1):103-12. doi: 10.1104/pp.43.1.103.
Two phosphorylases have been found in the endosperm of Zea mays. Phosphorylase I is found through all stages of endosperm development and seed germination investigated. The other enzyme, phosphorylase II appears only at the stage of rapid starch biosynthesis and is not found during germination. At 22 days after pollination, the activity of phosphorylase II is 10 times that of phosphorylase I. These 2 phosphorylases are separable by column chromatography and behave differently in several respects.Phosphorylase I cannot utilize maltose as a primer while phosphorylase II does so readily. Furthermore, phosphorylase II can synthesize an amylose-like polymer from a "primer free" system after a lag phase.Phosphorylase II is inhibited severely at pH 5.8 by ATP, GTP, ADP, and GDP, and less drastically by UTP, CTP, UDP and CDP. Phosphorylase I is somewhat inhibited by purine nucleotides but not by pyrimidine nucleotides. In all cases, the inhibition is pH-dependent. Phosphorylase I is inhibited competitively by ATP while phosphorylase II is inhibited non-competitively.Phosphorylase II is markedly stimulated by 10 mm Mg(2+) and by 2 mm ethylenediamine tetraacetic acid while phosphorylase I is relatively little affected.
在玉米胚乳中发现了两种磷酸化酶。磷酸化酶 I 存在于胚乳发育和种子萌发的所有阶段。另一种酶，磷酸化酶 II 仅在快速淀粉生物合成阶段出现，在萌发过程中未发现。授粉后 22 天，磷酸化酶 II 的活性是磷酸化酶 I 的 10 倍。这两种磷酸化酶可以通过柱层析分离，并且在几个方面表现出不同的行为。磷酸化酶 I 不能利用麦芽糖作为引物，而磷酸化酶 II 则可以轻易地做到这一点。此外，磷酸化酶 II 可以在延迟期后从“无引物”系统中合成类似淀粉的聚合物。磷酸化酶 II 在 pH5.8 时被 ATP、GTP、ADP 和 GDP 强烈抑制，被 UTP、CTP、UDP 和 CDP 稍微强烈抑制。磷酸化酶 I 被嘌呤核苷酸略有抑制，但不被嘧啶核苷酸抑制。在所有情况下，抑制作用都是 pH 依赖性的。磷酸化酶 I 被 ATP 竞争性抑制，而磷酸化酶 II 被非竞争性抑制。10mmMg(2+) 和 2mm 乙二胺四乙酸显著刺激磷酸化酶 II，而磷酸化酶 I 受影响较小。
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