Roles of Four Sorbitol Related Enzymes and Invertase in the Seasonal Alteration of Sugar Metabolism in Apple Tissue
Roles of Four Sorbitol Related Enzymes and Invertase in the Seasonal Alteration of Sugar Metabolism in Apple Tissue
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DOI：
10.21273/jashs.111.1.134
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发表时间：
1986-01
影响因子：
1.9
通讯作者：
S. Yamaki;Kazuko Ishikawa
中科院分区：
文献类型：
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作者：
S. Yamaki;Kazuko Ishikawa
研究了苹果山梨醇-6-P脱氢酶、NAD+依赖型山梨醇脱氢酶、NADP+依赖型山梨醇脱氢酶、山梨醇氧化酶和酸性转化酶的活性和作用。'Jonnagold'）的叶子和果实。几乎所有的可溶性碳水化合物在整个季节都以山梨糖醇的形式存在。在这些酶中，山梨醇-6-P脱氢酶的活性最高，在幼叶中较高，并随着年龄的增长而降低;而依赖于NAD+和NADP+的山梨醇脱氢酶和山梨醇氧化酶活性几乎检测不到。山梨醇从叶片转移到果实，在那里它很容易代谢成其他糖，所以山梨醇浓度没有增加。NAD+依赖的山梨醇脱氢酶将山梨醇转化为果糖，在果实发育过程中具有最高的4种酶活性。其活性在6月上升，在中期下降，并再次增加与果实成熟。酶活性的波动对应于果糖浓度的变化。山梨醇氧化酶活性随果实增大而增加，约为NAD+依赖型山梨醇脱氢酶活性的五分之一。叶片和果实中酸性转化酶活性明显高于山梨醇酶活性，但其在糖转运和代谢中的作用尚不清楚。山梨醇在茎和花序梗的水平保持相对恒定的季节表明，很少发生在运输过程中的韧皮部代谢。
Activities and roles of 4 sorbitol enzymes, sorbitol-6-P dehydrogenase, NAD+-dependent sorbitol dehydrogenase, NADP+-dependent sorbitol dehydrogenase and sorbitol oxidase, and acid invertase in apple (Malus domestica Borkh. ‘Jonnagold’) leaves and fruit were studied. Almost all of the soluble carbohydrates in leaves are present as sorbitol throughout the season. Sorbitol-6-P dehydrogenase had the highest activity among the enzymes, being high in young leaves and decreasing with age; whereas NAD+- and NADP+-dependent sorbitol dehydrogenases and sorbitol oxidase activities were barely detectable. Sorbitol was translocated from leaves to fruits where it was readily metabolized to other sugars, so the sorbitol concentration did not increase. NAD+-dependent sorbitol dehydrogenase that converts sorbitol to fructose had the highest activity of the 4 enzymes in developing fruits. Its activity rose in June, decreased in midseason, and increased again with fruit maturation. The fluctuation in enzyme activity corresponded to changes in fructose concentration. Sorbitol oxidase activity, which was about one-fifth that of NAD+-dependent sorbitol dehydrogenase, increased proportionately as fruits enlarged. Acid invertase activity was distinctly higher than sorbitol enzyme activities in both leaves and fruit, but its roles in sugar translocation and metabolism were not clearly established. The levels of sorbitol in stems and peduncles remained relatively constant during the season indicating that little metabolism occurred in the phloem during transit.