Red River Valley Potato Processing Laboratory , East Grand Forks, Minnesota 56721.
Plant Physiol. 1969 May;44(5):759-64. doi: 10.1104/pp.44.5.759.
Sucrose synthetase activity is high in young potato tubers but decreases markedly during maturation. The activity decreases rapidly after the tubers are harvested and remains low regardless of storage temperature. This enzyme was purified 34-fold from freshly harvested immature potatoes. It catalyzes both cleavage and synthesis of sucrose but the 2 activities differ in a number of ways. The pH optima are 6.6 and 8.8 for sucrose cleavage and synthesis. respectively. Sucrose cleavage is activated 4-fold by mercaptoethanol and is inhibited by Mn(2+). In contrast, sucrose synthesis is activated only slightly by either mercaptoethanol or Mn(2+) alone but 2-fold in the presence of both reagents. However, it was not possible to resolve the 2 activities, their stabilities to partial thermal inactivation are identical, and their ratios are constant over a wide range of activities.
蔗糖合酶在幼嫩的土豆块茎中活性很高，但在成熟过程中显著下降。块茎收获后，其活性迅速下降，无论储存温度如何，活性都保持较低水平。该酶可从刚收获的未成熟土豆中纯化 34 倍。它既能催化蔗糖的裂解又能催化蔗糖的合成，但这两种活性在许多方面存在差异。蔗糖裂解和合成的最适 pH 值分别为 6.6 和 8.8。巯基乙醇使蔗糖裂解活性提高 4 倍，并被 Mn(2+)抑制。相比之下，只有巯基乙醇或 Mn(2+)单独存在时，蔗糖合成活性才略有增加，但在两种试剂同时存在时增加 2 倍。然而，这两种活性无法分开，它们对部分热失活的稳定性是相同的，并且在广泛的活性范围内其比值是恒定的。
