Matsuo N, Kaneko S, Kuno A, Kobayashi H, Kusakabe I
Central Research Laboratory, Godo Shusei Co. Ltd., Kamihongo, Matsudo, Chiba 271-0064, Japan.
Biochem J. 2000 Feb 15;346 Pt 1(Pt 1):9-15.
alpha-L-Arabinofuranosidases I and II were purified from the culture filtrate of Streptomyces chartreusis GS901 and were found to have molecular masses of 80 and 37 kDa and pI values of 6.6 and 7.5 respectively. Both enzymes demonstrated slight reactivity towards arabinoxylan and arabinogalactan as substrates but did not hydrolyse gum arabic or arabinoxylo-oligosaccharides. alpha-L-Arabinofuranosidase I hydrolysed all of the alpha-linkage types that normally occur between two alpha-L-arabinofuranosyl residues, with the following decreasing order of reactivity being observed for the respective disaccharide linkages: alpha-(1-->2) alpha-(1-->3) alpha-(1-->5). This enzyme cleaved the (1-->3) linkages of the arabinosyl side-chains of methyl 3, 5-di-O-alpha-L-arabinofuranosyl-alpha-L-arabinofuranoside in preference to the (1-->5) linkages. alpha-L-Arabinofuranosidase I hydrolysed approx. 30% of the arabinan but hydrolysed hardly any linear arabinan. In contrast, alpha-L-Arabinofuranosidase II hydrolysed only (1-->5)-arabinofuranobioside among the regioisomeric methyl arabinobiosides and did not hydrolyse the arabinotrioside. Linear 1-->5-linked arabinan was a good substrate for this enzyme, but it hydrolysed hardly any of the arabinan. Synergism between the two enzymes was observed in the conversion of arabinan and debranched arabinan into arabinose. Complete amino acid sequencing of alpha-L-arabinofuranosidase I indicated that the enzyme consists of a central catalytic domain that belongs to family 51 of the glycoside hydrolases and additionally that unknown functional domains exist in the N-terminal and C-terminal regions. The amino acid sequence of alpha-L-arabinofuranosidase II indicated that this enzyme belongs to family 43 of the glycoside hydrolase family and, as this is the first report of an exo-1, 5-alpha-L-arabinofuranosidase, it represents a novel type of enzyme.
α-L-阿拉伯呋喃糖苷酶I和II从绿灰链霉菌GS901的培养滤液中纯化得到，发现它们的分子量分别为80 kDa和37 kDa，pI值分别为6.6和7.5。两种酶对阿拉伯木聚糖和阿拉伯半乳聚糖作为底物均表现出轻微反应性，但不水解阿拉伯树胶或阿拉伯木糖寡糖。α-L-阿拉伯呋喃糖苷酶I水解了通常存在于两个α-L-阿拉伯呋喃糖基残基之间的所有α-连接类型，对于各自的二糖连接，观察到以下反应性递减顺序：α-(1→2)＞α-(1→3)＞α-(1→5)。该酶优先切割3,5-二-O-α-L-阿拉伯呋喃糖基-α-L-阿拉伯呋喃糖苷的阿拉伯糖基侧链的(1→3)连接，而不是(1→5)连接。α-L-阿拉伯呋喃糖苷酶I水解了约30%的阿拉伯聚糖，但几乎不水解任何线性阿拉伯聚糖。相比之下，α-L-阿拉伯呋喃糖苷酶II仅水解区域异构体甲基阿拉伯二糖苷中的(1→5)-阿拉伯呋喃二糖苷，不水解阿拉伯三糖苷。线性1→5连接的阿拉伯聚糖是该酶的良好底物，但它几乎不水解任何阿拉伯聚糖。在将阿拉伯聚糖和去支链阿拉伯聚糖转化为阿拉伯糖的过程中观察到了两种酶之间的协同作用。α-L-阿拉伯呋喃糖苷酶I的完整氨基酸序列表明，该酶由一个属于糖苷水解酶家族51的中央催化结构域组成，此外在N端和C端区域存在未知功能结构域。α-L-阿拉伯呋喃糖苷酶II的氨基酸序列表明，该酶属于糖苷水解酶家族43，并且由于这是外切-1,5-α-L-阿拉伯呋喃糖苷酶的首次报道，它代表了一种新型酶。
