Department of Agricultural Chemistry, Kyushu University, Fukuoka 812, Japan.
Appl Environ Microbiol. 1988 Jun;54(6):1523-9. doi: 10.1128/aem.54.6.1523-1529.1988.
Two immunologically related cellobiohydrolases, cellobiohydrolase I (CBH I) and cellobiohydrolase II (CBH II), were purified from Aspergillus ficum. The Avicel-adsorbable CBH I (molecular weight, 128,000) digested Avicel, cotton, and cellulose powder to cellobiose, but the Avicel-unadsorbable CBH II (molecular weight, 50,000) could not digest those substrates. Both enzymes hydrolyzed insoluble cellooligosaccharides (DP 25) to cellobiose. High-pressure liquid chromatographic analysis of soluble cellooligosaccharide hydrolysates revealed that both enzymes split off strictly cellobiose units from the nonreducing end of the cellulose chain with an exowise mechanism. CBH I showed glucosyltransferase activity, but CBH II did not. The N-bromosuccinimideoxidized CBH I was completely inactive but retained the ability to adsorb to Avicel. This suggested that CBH I has separate sites for binding to cellulose and for catalyzing cleavage of glycosidic linkages. Cellobiohydrolases were of two types, CBH I and CBH II. The former can adsorb to and digest Avicel, while the latter can do neither.
两种免疫相关的纤维二糖水解酶，纤维二糖水解酶 I（CBH I）和纤维二糖水解酶 II（CBH II），从曲霉菌中纯化而来。可被微晶纤维素吸附的 CBH I（分子量为 128000）可将微晶纤维素、棉花和纤维素粉水解为纤维二糖，但不可被微晶纤维素吸附的 CBH II（分子量为 50000）则不能水解这些底物。两种酶均能将不溶性纤维寡糖（DP 25）水解为纤维二糖。高效液相色谱分析可溶性纤维寡糖水解产物表明，两种酶均以外切方式从纤维素链的非还原端依次切割下纤维二糖单元。CBH I 表现出葡萄糖基转移酶活性，但 CBH II 没有。N-溴代丁二酰亚胺氧化的 CBH I 完全失活，但仍保留吸附微晶纤维素的能力。这表明 CBH I 具有分别结合纤维素和催化糖苷键裂解的活性位点。纤维二糖水解酶有两种类型，CBH I 和 CBH II。前者可吸附并消化微晶纤维素，而后者则不能。
