Department of Fruit Trees (Subtropical and Deciduous), Agricultural Research Organization, The Volcani Centre, Bet Dagan 50250, Israel.
Plant Physiol. 1986 May;81(1):130-5. doi: 10.1104/pp.81.1.130.
Preclimacteric avocado (Persea americana Mill.) fruits produced very little ethylene and had only a trace amount of l-aminocyclopropane-1-carboxylic acid (ACC) and a very low activity of ACC synthase. In contrast, a significant amount of l-(malonylamino)cyclopropane-1-carboxylic acid (MACC) was detected during the preclimacteric stage. In harvested fruits, both ACC synthase activity and the level of ACC increased markedly during the climacteric rise reaching a peak shortly before the climacteric peak. The level of MACC also increased at the climacteric stage. Cycloheximide and cordycepin inhibited the synthesis of ACC synthase in discs excised from preclimacteric fruits. A low but measurable ethylene forming enzyme (EFE) activity was detected during the preclimacteric stage. During ripening, EFE activity increased only at the beginning of the climacteric rise. ACC synthase and EFE activities and the ACC level declined rapidly after the climacteric peak. Application of ACC to attached or detached fruits resulted in increased ethylene production and ripening of the fruits. Exogenous ethylene stimulated EFE activity in intact fruits prior to the increase in ethylene production. The data suggest that conversion of S-adenosylmethionine to ACC is the major factor limiting ethylene production during the preclimacteric stage. ACC synthase is first synthesized during ripening and this leads to the production of ethylene which in turn induces an additional increase in ACC synthase activity. Only when ethylene reaches a certain level does it induce increased EFE activity.
未成熟鳄梨（Persea americana Mill.）果实产生的乙烯很少，l-氨基环丙烷-1-羧酸（ACC）和 ACC 合酶的活性也很低。相比之下，在未成熟阶段检测到相当数量的 l-（丙氨酰氨基）环丙烷-1-羧酸（MACC）。在收获的果实中，ACC 合酶活性和 ACC 水平在成熟高峰期急剧上升，在成熟高峰期前不久达到峰值。MACC 水平也在成熟阶段增加。环己酰亚胺和虫草素抑制了从未成熟果实中分离出来的圆盘的 ACC 合酶合成。在未成熟阶段检测到低但可测量的乙烯形成酶（EFE）活性。在成熟过程中，EFE 活性仅在成熟高峰期开始时增加。ACC 合酶和 EFE 活性以及 ACC 水平在成熟高峰期后迅速下降。将 ACC 应用于附着或未附着的果实会导致果实产生更多的乙烯并成熟。外源乙烯在乙烯产生增加之前刺激完整果实中的 EFE 活性。数据表明，在未成熟阶段限制乙烯产生的主要因素是 S-腺苷甲硫氨酸转化为 ACC。ACC 合酶在成熟过程中首先合成，这导致乙烯的产生，而乙烯又诱导 ACC 合酶活性的进一步增加。只有当乙烯达到一定水平时，它才会诱导增加的 EFE 活性。
