Fritz Macarena, Ravanal María Cristina, Braet Christophe, Eyzaguirre Jaime
Departamento de Ciencias Biológicas, Universidad Andrés Bello, República 217, Santiago, Chile.
Mycol Res. 2008 Aug;112(Pt 8):933-42. doi: 10.1016/j.mycres.2008.01.022. Epub 2008 Feb 16.
The soft rot fungus Penicillium purpurogenum secretes a wide variety of xylanolytic enzymes to the medium, among them three alpha-l-arabinofuranosidases. This work refers to arabinofuranosidase 2 (ABF 2). This enzyme was purified to homogeneity and characterized; it is a glycosylated monomer with a molecular weight of 70 000 and an isoelectric point of 5.3. When assayed with p-nitrophenyl alpha-l-arabinofuranoside (pNPAra) the enzyme followed Michaelis-Menten kinetics with a K(M) of 0.098mm. The optimum pH is 5 and the optimal temperature 60 degrees C. ABF 2 showed weak activity on natural polymeric substrates, such as sugar beet arabinan, debranched arabinan, and arabinoxylan. These results, together with its low K(M) (pNPAra) and its activity towards short arabinooligosaccharides, suggest that the enzyme belongs to the exo alpha-l-arabinosyl hydrolases not active on polymers. The abf2 gene and its cDNA were sequenced, and the gene was found to possess seven introns. The mature protein is 618 amino acids long with a calculated molecular weight of 67 212. Amino acid sequence alignments show that the enzyme belongs to family 51 of the glycosyl hydrolases, although it differs in some properties from other enzymes of this family.
产紫青霉这种软腐真菌可向培养基中分泌多种木聚糖分解酶，其中包括三种α-L-阿拉伯呋喃糖苷酶。本研究涉及阿拉伯呋喃糖苷酶2（ABF 2）。该酶已被纯化至同质并进行了特性鉴定；它是一种糖基化单体，分子量为70000，等电点为5.3。用对硝基苯基α-L-阿拉伯呋喃糖苷（pNPAra）进行测定时，该酶遵循米氏动力学，K(M)为0.098mm。最适pH为5，最适温度为60℃。ABF 2对天然聚合物底物，如甜菜阿拉伯聚糖、去支链阿拉伯聚糖和阿拉伯木聚糖，显示出较弱的活性。这些结果，连同其较低的K(M)（pNPAra）以及对短阿拉伯低聚糖的活性，表明该酶属于对聚合物无活性的外切α-L-阿拉伯糖基水解酶。对abf2基因及其cDNA进行了测序，发现该基因含有七个内含子。成熟蛋白长度为618个氨基酸，计算分子量为67212。氨基酸序列比对表明，该酶属于糖基水解酶家族51，尽管它在某些特性上与该家族的其他酶不同。
