The xylan-degrading enzyme system of Talaromyces emersonii: novel enzymes with activity against aryl β-d-xylosides and unsubstituted xylans

Abstract

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.

Mitochondrial malate dehydrogenase from the thermophilic, filamentous fungus Talaromyces emersonii

“…3). Through other studies conducted in this laboratory [20,22,23], T. emersonii is known to produce an array of extracellular carbohydrate-modifying enzymes that can depolymerize pectin polysaccharides. Production of these enzymes during growth on citrus pectin may provide a continuous supply of readily metabolized sugars, which may explain the consistent expression of the m-MDH gene throughout the specified growth period.…”

“…T. emersonii is distinguished from thermotolerant counterparts by its growth temperature range of 30-65°C and ability to thrive at growth temperatures between 45 and 55°C (data from our laboratory and [17]). Work conducted in our laboratory has revealed that T. emersonii produces a potent array of complete, multicomponent enzyme systems that degrade key biopolymers in nature, including proteins and various terrestrial and marine plant carbohydrates [18][19][20][21][22][23][24]. In addition, more recent studies have revealed that T. emersonii may be a Pandora's box of other interesting glycosyl hydrolases and oxidoreductases, many of which have homologs in model eukaryotic species [25,26].…”

Purification and characterization of a ferulic acid esterase (FAE-III) from Aspergillus niger: specificity for the phenolic moiety and binding to microcrystalline cellulose

“…Groups of enzymes are arranged into 'systems', such as xylan-degrading (Tuohy et al, 1993;Myburgh e t al., 1991 ; Johnson e t a/., 1988) and cellulose-degrading (Beguin e t al., 1992;Wood, 1992). The nature of these enzyme-substrat:e interactions and cooperativity between enzymes are presently the subject of extensive research, especially concerning the breakdown of cellulose and hemicellulose , because of possible exploitation in agricultural and industrial processes .…”

Characterization of a multimeric, eukaryotic prolyl aminopeptidase: an inducible and highly specific intracellular peptidase from the non-pathogenic fungus Talaromyces emersonii

“…It has generally recognized as safe (GRAS) status, making it a biotechnologically relevant organism to rival Aspergillus and Trichoderma species for the production of important industrial enzymes. T. emersonii has been shown to secrete a wide array of hydrolytic enzymes under defined growth conditions, and possesses complete xylan-and cellulasedegrading systems that consist of diversified carbohydrases (Heneghan et al, 2007;Murray et al, 2001Murray et al, , 2003Reen et al, 2003;Tuohy et al, 1993Tuohy et al, , 1994Tuohy et al, , 2002. Previously, we have shown that the presence of peptides in growth media induces expression of an extracellular peptidase with broad substrate specificity in T. emersonii (O'Donoghue et al, 2008).…”