Purification and characterization of β-xylosidase from potatoes (Solanum tuberosum)

Potatoes are a cheap and easily available source for the preparation of 1,2-xylosidase, The soluble enzyme was purified from potato tubers by ammonium sulfate precipitation, hydrophobic interaction chromatography, affinity gel blue chromatography, ion exchange and size exclusion chromatography yielding a glycoprotein with a molecular weight of 39-40 kDa, an isoelectric point of 5.1 and a typical plant N-glycosylation pattern. The enzyme releases xylose residues beta1,2-linked to the beta-mannose of an N-glycan core, if the 3-position of this mannose is not occupied. It showed an optimal enzymatic activity at pH 4.0-4.5 and at a temperature of 50 degreesC. The activity was reduced in the presence of Ni2+ and Cu2+ and slightly increased by the addition of Mn2+ or Ca2+. At 37 degreesC the cleavage of xylose from p-nitrophenyl-xylopyranoside or appropriate pyridylaminated N-glycans was proportional to the time of incubation over a period of 8 h and increased with time for at least 24 h. N-Methoxycarbonylpentyl-1,5-dideoxy-1,5-iminoxylitol inhibits the enzyme effectively. Sequencing of the N-terminus showed a high homology to a number of isoforms of patatin, the main protein of potato tubers. This enzyme will be an important tool for the analysis of N-glycans and in the modification of N-glycans for immunological studies. (C) 2004 Elsevier B.V. All rights reserved.