Tuohy M G, Puls J, Claeyssens M, Vrsanská M, Coughlan M P
Department of Biochemistry, University College, Galway, Ireland.
Biochem J. 1993 Mar 1;290 ( Pt 2)(Pt 2):515-23. doi: 10.1042/bj2900515.
Talaromyces emersonii, a thermophilic aerobic fungus, produces a complete xylan-degrading enzyme system when grown on appropriate substrates. In this paper we present the physicochemical and catalytic properties of three enzymes, xylosidase (Xyl) I (M(r) 181,000; pI 8.9), II (M(r) 131,000; pI 5.3) and III (M(r) 54,200; pI 4.2). Xyl I and II appear to be dimeric and Xyl III is a single-subunit protein. All three enzymes catalyse the hydrolysis of aryl beta-D-xylosides and xylo-oligosaccharides. Xyl I is a classic beta-xylosidase (1,4-beta-D-xylan xylohydrolase; EC 3.2.1.37), and Xyl II and III are novel xylanases (endo-1,4-beta-D-xylan xylanohydrolase; EC 3.2.1.8) which we believe have not hitherto been reported. In addition to the above substrates, they also catalyse the extensive hydrolysis of unsubstituted xylans, and may have considerable biotechnological potential. The hydrolysis product profiles and bond-cleavage frequencies with various substrates are presented.
艾默生篮状菌是一种嗜热需氧真菌，在合适的底物上生长时会产生完整的木聚糖降解酶系统。本文介绍了三种酶的物理化学性质和催化特性，即木糖苷酶（Xyl）I（相对分子质量181,000；等电点8.9）、II（相对分子质量131,000；等电点5.3）和III（相对分子质量54,200；等电点4.2）。Xyl I和II似乎是二聚体，Xyl III是单亚基蛋白。这三种酶都能催化芳基β-D-木糖苷和木寡糖的水解。Xyl I是一种典型的β-木糖苷酶（1,4-β-D-木聚糖木糖水解酶；EC 3.2.1.37），Xyl II和III是新型木聚糖酶（内切-1,4-β-D-木聚糖木聚糖水解酶；EC 3.2.1.8），我们认为此前尚未有相关报道。除上述底物外，它们还能催化未取代木聚糖的大量水解，可能具有相当大的生物技术潜力。文中给出了各种底物的水解产物谱和键断裂频率。
