NetNGly 1.0 predicted 12 potential N-glycosylation sites for β-xylosidase, and consistent with this, the recombinant enzyme was heterogeneous with a molecular mass estimated between 153 and 165 kDa on SDS-PAGE (Figure 1).
A controversial difference occurs between the molecular mass generally considered in the literature for β-conglutin (180 200 kDa) and the apparent native molecular mass estimated by FPLC gel filtration on a Superose column for the native protein containing blad as 210 kDa.
The average molecular mass estimated by mass spectrometry was 14,156.5 for pMTX-I, 14,249.5 for pMTX-II, and 14,253.0 for pMTX-III.
Native PrTX-III subjected to molecular mass exclusion chromatography showed the presence of a main fraction with a molecular mass that was estimated at 25,000 Da and a minor fraction with molecular mass estimated at 14,000 Da.
In this case, the molecular mass, estimated from the sedimentation data, is 21 kDa, whereas the theoretical value is 22 kDa.
The chromatographic profile of PrTX-III: HP-2 revealed the presence of a main fraction, which had its molecular mass estimated at 14,000 Da, and a minor fraction with molecular mass of 20,000 Da.
The 18-kDa fragment produced by chymotrypsin was identified as the N-terminal region including residues 1 172, with an expected molecular mass of 19.6 kDa, which is consistent with the apparent molecular mass estimated by SDS/PAGE.
Sanghvi et al. [ 7] partially purified a xylanase from T. harzianum with 29.0 kDa molecular mass, while 27.0 kDa was the molecular mass estimated for the xylanase from Penicillium sp. [ 8].
The deduced amino acid sequence of the full-length enzyme consists of 583 residues (including the N-terminal histidine tag) corresponding to a molecular mass of 65978.6 Da, which is in accordance with the apparent molecular mass estimated by SDS PAGE.
