【摘要】 利用DEAE—纤维素柱层析对白兰瓜子叶蔗糖酶同工酶进行了分离。发现细胞质可溶性部分含有4种蔗糖酶同工酶,其中3种为酸性蔗糖酶(Ⅰ、Ⅱ、Ⅲ),其活性最适pH分别为5.40、4.30和4.73;另外一种为碱性蔗糖酶,其最适pH为7.40。细胞壁盐溶性部分仅含1种酸性蔗糖酶,其最适pH亦为4.73。在白兰瓜子叶生长后期(7～11d),定位于细胞质的酸性蔗糖酶Ⅰ、Ⅱ和Ⅲ的活性略有升高;衰老发生后(17～23d)其活性显著下降;衰老后期碱性蔗糖酶活性消失。在子叶生长和衰老期间细胞壁酸性蔗糖酶活性则一直下降。更多还原

【Abstract】 The invertase isoenzymes of cotyledonsof Bailan melon seedlings and its rela-tion to cotyledon senescence had beenstudied. The results indicated that therewere five kinds of invertase isoenzymesin Bailan melon cotyledons, whichcould be distinguished by their pH opti-ma, chromatographic behavior onDEAE-cellulose and intracellular loca-tion. Cytosolic (soluble) invertase Ⅰ,Ⅱ, Ⅲ and Ⅳ exhibited pH optima5. 40, 4. 30, 4. 73 and 7. 40, respec-tively (Fig. 2). Cell wall-bound inver-tase also exhibited pH optimum 4. 73.The alkaline invertase (isoenzyme Ⅳ)was only present in cytoplasm, whereasacid invertase was present in both cyto-plasm and cell wall. The activities of acid-invertase(isoenzyme Ⅰ, Ⅱ and Ⅲ) in cyto-plasm slightly increased in the later stageof growth (from day 7 to dey 11) anddecreased markedly after the onset ofsenescence (from day 17 to day 23).The activity of alkaline invertase in cy-toplasm continued to rise until the medi-um stage of senescence, and suddenlydisappeared at day 23. After the onsetof senescence, the activity of cell wall-bound acid invertase decreased marked-ly. The decline of invertases (especiallyacid invertases) led to the sharp accu-mulation of sucrose during the latesenescence (Fig. 4), this in turn en-hanced the process of cotyledon senes-cence. Therefore, it seems that the acidinvertases play important roles duringsenescence of cotyledons of Bailan mel-on seedlings.更多还原