Nucleoside Diphosphate Sugar-Starch Glucosyl Transferase Activity of wx Starch Granules.
Nucleoside Diphosphate Sugar-Starch Glucosyl Transferase Activity of wx Starch Granules.
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wx 淀粉颗粒的核苷二磷酸糖-淀粉葡萄糖基转移酶活性。
DOI：
10.1104/pp.62.3.383
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发表时间：
1978
期刊：
影响因子：
7.4
通讯作者：
M. T. Chang
中科院分区：
文献类型：
--
作者：
O. Nelson;P. Chourey;M. T. Chang
从所有蜡质玉米（Zea mays L.）突变体的胚乳组织中制备的淀粉颗粒，将二磷酸腺苷葡萄糖转化为淀粉的能力都很低，但大致相同。然而，随着底物浓度的降低，蜡质制剂相对于非突变体的活性增加，直到使用最低底物浓度（0.1 muM）时，蜡质制剂的活性几乎与非突变体制剂相等。从wx-C/wx-C/wx-C胚乳制备淀粉颗粒的表观K(m)（二磷酸腺苷葡萄糖）为7.1 × 10(-5) m，而从非蜡质胚乳制备淀粉颗粒的表观K(m)为3 × 10(-3) m。在给定的底物浓度下，从其他三个独立突变来源的蜡质突变体制备的淀粉颗粒具有大约等于wx-C的酶活性水平，从而产生相似的表观K(m)估计值。我们得出结论，在玉米胚乳淀粉颗粒中存在第二种淀粉颗粒结合的糖基转移酶，当突变消除了催化相同反应的更活跃的糖基转移酶的活性时，它的存在被揭示出来。
Starch granule preparations from the endosperm tissue of all waxy maize (Zea mays L.) mutants tested have low and approximately equal capability to incorporate glucose from adenosine diphosphate glucose into starch. As the substrate concentration is reduced, however, the activity of waxy preparations relative to nonmutant increases until, at the lowest substrate concentration utilized (0.1 muM), the activity of the waxy preparations is nearly equal to that of the nonmutant preparation. The apparent K(m) (adenosine diphosphate glucose) for starch granule preparations from wx-C/wx-C/wx-C endosperms was 7.1 x 10(-5) M, which is compared to 3 x 10(-3) M for preparations from nonwaxy endosperms. Starch granule preparations from three other waxy mutants of independent mutational origin have levels of enzymic activity approximately equal to wx-C at a given substrate concentration giving rise to similar apparent K(m) estimates. We conclude that there is in maize endosperm starch granules a second starch granule-bound glycosyl transferase, whose presence is revealed when mutation eliminates activity of the more active glucosyl transferase catalyzing the same reaction.