A BETA-GALACTOSIDASE FROM RADISH (RAPHANUS-SATIVUS L) SEEDS
A BETA-GALACTOSIDASE FROM RADISH (RAPHANUS-SATIVUS L) SEEDS
复制标题
DOI：
10.1104/pp.90.2.567
复制
发表时间：
1989-06-01
期刊：
影响因子：
7.4
通讯作者：
YAMAMOTO, S
中科院分区：
文献类型：
--
作者：
SEKIMATA, M;OGURA, K;YAMAMOTO, S
一个基本的β-半乳糖苷酶（β-半乳糖酶（Galase）从萝卜（Raphanus sativus L.）种子通过常规纯化程序。纯化的酶是一种由单一多肽组成的蛋白质，其表观分子量为45千道尔顿，pI值为8.6至8.8。该酶在pH4.0时对对硝基苯基β-氨基苯甲酸具有最大活性。D-半乳糖苷和β- 1，3-连接半乳糖二糖。Hg ~（2+）和4-氯汞苯甲酸盐对酶活性有强烈的抑制作用。D-半乳糖-（1 → 4）-内酯和D-半乳糖醛作为有效的竞争性抑制剂。使用连接类型不同的低聚半乳糖作为底物，证明了萝卜种子β- Galase特别分离出β- 1，3和β1，6-连接的D-半乳糖残基从非还原性末端，和它们的水解率增加，增加链长。萝卜种子和叶阿拉伯-3，6-半乳聚糖蛋白对β-半乳糖苷酶具有抗性。但在用真菌α-半乳糖酶处理后可被该酶部分降解。L-阿拉伯呋喃糖苷酶留下一些由D-半乳糖、糖醛酸、L-阿拉伯糖和除D-半乳糖之外的其他次要糖组分组成的寡糖作为主要产物。
A basic .beta.-galactosidase (.beta.-Galase) has been purified 281-fold from imbibed radish (Raphanus sativus L.) seeds by conventional purification procedures. The purified enzyme is an electrophoretically homogenous protein consisting of a single polypeptide with an apparent molecular mass of 45 kilodaltons and pI values if 8.6 to 8.8. The enzyme was maximally active at pH 4.0 on p-nitrophenyl .beta.-D-galactoside and .beta.-1,3-linked galactobiose. The enzyme activity was inhibited strongly by Hg2+ and 4-chloromercuribenzoate. D-Galactono-(1.fwdarw.4)-lactone and D-galactal acted as potent competitive inhibitors. Using galactooligosaccharides differing in the types of linkage as the substrates, it was demonstrated that radish seed .beta.-Galase specifically split off .beta.-1,3- and .beta.-1,6-linked D-galactosyl residues from the nonreducing ends, and their rates of hydrolysis increased with increasing chain lengths. Radish seed and leaf arabino-3,6-galactan-proteins were resistant to the .beta.-galase alone but could be partially degraded by the enzyme after the treatment with a fungal .alpha.-L-arabinofuranosidase leaving some oligosaccharides consisting of D-galactose, uronic acid, L-arabinose, and other minor sugar components besides D-galactose as the main product.