P-xylosidase

Redox reaetions and hydrolysis are the predominant metabolie eonversions triggered by the intestinal microflora. The main reductive enzymes produeed by the intestinal mieroflora are nitroreductase, deaminase, urea dehydroxylase, and azoreduetase the hydrolytic enzymes are P-glucoronidase, P-xylosidase, P-galaetosidase, and a-L-arabinosidase. Studies conducted by Macfarlane and co-workers have shown that proteolysis ean also happen in the colon [31]. More recent findings by this group indieate that bacterial fermentation of proteins in humans could account for 17% of... 

V. Patel and A. L. Tappel, Identity of P-glucosidase and P-xylosidase activities in rat liver lysosomes, Biochim. Biophys. Acta Enzymol., 191 (1969) 653-662. 

The complete degradation of hemicellulose becomes more complex than that of cellulase, since substituent-hydrolyzing activities are also necessary. With heteroxylans, apart from endo-l,4- 3-xylanase, which catalyzes the hydrolysis of internal 3-l,4-xylan links and P-xylosidase, which catalyzes the hydrolysis of xylooligossacharides, mainly xylobiose into xylose, other enzymes must act to accomplish complete hydrolysis, such as acetyl xylan esterase, a-glucuronidase, and a-L-arabinofuranosidase (1). 

Unlike starch or cellulose, BSG hemicellulose has a complex structure, which is still present, in part, on its autohydrolysis products. Oligosaccharides from BSG hydrolysis consist mainly of branched arabino-xylo-glucurono oligosaccharides that are not highly acetylated when compared to other xylans, such as from Eucalyptus wood (31). The action of several enzymatic activities including endo-l,4-P-xylanase P-xylosidase and accessory activities such as acetyl xylanesterase, a-glucuronidase, and a-arabino-furanosidase is therefore required for the complete hydrolysis of OCL to monosaccharides. 

Besides these factors, the synthetic nitrophenyl derivatives used for estimating P-xylosidase, acetyl xylanesterase, and a-arabinofuranosidase activities may not provide suitable information to be applied to a real, complex substrate and/or additional enzymes (such as a-glucuronidases)... 

Enzyme formulations P-xylanase P-xylosidase Acetyl esterase a-arabino- furanosidase FPase Glucose Xylose Arabinose Acetic Acid... 

Many tissues from patients with I-cell disease exhibit normal levels of intracellular lysosomal enzymatic activities (e.g., brain, liver, kidney, and spleen). In the liver, lysosomal enzyme levels are normal except for diminished P-galactosidase and elevated P-hexosaminidase, P-xylosidase.and a-galactosidase. This fairly spe-... 

Iembo, T., Azevedo, M. O., Bloch Jr., C., and Filho, E. X. F. 2006. Purification and partial characterization of a new P-xylosidase from Humicola grisea var. thermoidea. World J. Microbiol. Biotechnol, 22, 415-419. 

Kitpreechavanich, V., Srisuk, and Lotong, N. 1992. Production of P-xylanase and P-xylosidase by Aspergillus fumigatus using solid state cuhtvation. In Visser, J., Beldman, G., Kusters-van Someren, M. A., and Voragen, A. G. J. (Eds.), Xylan and xylanases (pp. 519-522). Amsterdam Elsevier Science Publishers. 

P-Xylosidases are being used commonly in paper industry for complete degradation of xylans. The enzymes used in the synthesis of xylose-containing compounds have also been reported. For example, Eneyskaya et al. (50) have used />-nitrophenyl P-D-xylopyranosides (XyiPpNP) as a donor and a 3-xylosidase ixom Aspergillus sp. in the synthesis of several 31,4-D-xylooli-gosaccharides as P-xylanase substrates. 

Eneyskaya EV, Brumer H, Backinowsky LV, Ivanen DR, Kul-minskaya AA, Shabalin KA, Neustroev KN. Enzymatic synthesis of P-xylanase substrates transglycosylation reactions of the P-xylosidase from Aspergillus sp. Carbohydr. Res. 2003 338 313-325. 

Castanospermine a-glucosidases (including amyloglucosidase, sucrase. maltase, isomaltase, trehalase, amylase, Glucosidase I and II) and p-glucosidases (including lactase and cellobiase), P-glucocerebrosidase and p-xylosidase ... 

T. Kasumi, Y. Tsumuraya, C. F. Brewer, H. Kersters-Hilderson, M. Claeyssens, and E. S. Hehre, Catalytic versatility of Bacillus pumilus P-xylosidase Glycosyl transfer and hydrolysis promoted with a- and P-D-xylosyl fluoride. Biochemistry 26 3010 (1987). 

Careful analysis of the kinetics of acid-base catalytic mutants can reveal essential ionisations not readily apparent in the wt. Glycosylation, rather than deglycosylation, was rate limiting for the acid-base El60A mutant of the GH 39 p-xylosidase of Thermoanaerobacterium saccharolyticum acting on aryl xylosides. The pH-rate profile was a similar bell-shape to wt, but shifted to more alkaline pH. It was suggested that an auxiliary carboxylate was acting as an acid-base catalyst in the mutant and that the pH-rate profile reflected a reverse protonation mechanism. 

Because of the heterogeneity of xylan, its hydrolysis requires the action of a xylanolytic enzyme system which is composed of P-l,4-endoxylanase (E.C. 3.2.1.8), P-xylosidase (E.C. 3.2.1.37), a-L-arabinofuranosidase (E.C. 3.2.1.55), a-glucuroni-dase (E.C. 3.2.1.-) and acetyl xylan esterase (E.C. 3.1.1.6) activities (Table 11.4-3). The concerted action of these enzymes converts xylan to its constituent sugars (Fig. 11.4-6). Xylan-degrading enzymes have been reported to be present in marine and... 

Organism Endoxylanase P-Xylosidase a-t-Arabino furanosldase a-Glucuro- nidase Acetyl xylan esterase... 

Flores, M. E., Perea, M., Rodriguez, O., Malvaez, A., Huitron, C. (1996). Physiological studies on induction and catabolite repression of p-xylosidase and endoxylanase in Streptomyces sp. CH-M-1035. Journal of Biotechnology, 49, 179-187. 

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