Biochemical and structural characterization of TLXI, the Triticum aestivum L. thaumatin-like xylanase inhibitor

Abstract

Thaumatin-like xylanase inhibitors (TLXI) are recently discovered wheat proteins. They belong to the family of the thaumatin-like proteins and inhibit glycoside hydrolase family 11 endoxylanases commonly used in different cereal based (bio)technological processes. We here report on the biochemical characterisation of TLXI. Its inhibition activity is temperature-and pH-dependent and shows a maximum at approximately 408C and pH 5.0. The TLXI structure model, generated with the crystal structure of thaumatin as template, shows the occurrence of five disulfide bridges and three b-sheets. Much as in the structures of other short-chain thaumatin-like proteins, no a-helix is present. The circular dichroism spectrum of TLXI confirms the absence of a-helices and the presence of antiparallel b-sheets. All ten cysteine residues in TLXI are involved in disulfide bridges. TLXI is stable for at least 120 min between pH 1-12 and for at least 2 hours at 1008C, making it much more stable than the other two xylanase inhibitors from wheat, i.e. Triticum aestivum xylanase inhibitor (TAXI) and xylanase inhibitor protein (XIP). This high stability can probably be ascribed to the high number of disulfide bridges, much as seen for other thaumatin-like proteins.

Isolation and Biochemical Characterization of Mucus Proteins in Japanese Bunching Onion (<i>Allium fistulosum</i>) Green Leaves

“…Most TLPs have molecular masses ranging from 21 to 26 kDa and contain 16 conserved cysteine residues, which form intramolecular disulfide bonds and contribute high stability under thermal and pH conditions (Fierens et al, 2009). The high stability of TLPs agrees with the residual activity of the mucus protein after heat treatment (Fig.…”

Characterization of a Pathogen Induced Thaumatin-Like Protein Gene AdTLP from Arachis diogoi, a Wild Peanut

“…Molecular mass of TLPs ranges between 21 to 26 kDa with a thaumatin family signature G-X- [GF]-X-C-X-T- [GA]-D-C-X- (1,2)-G-X-(2,3)-C [6]. In general, TLPs have 16 conserved cysteine residues that are involved in the formation of eight disulfide linkages, which impart stability to the protein under varied thermal and pH conditions [7,8]. …”

Temperature Resistance of Xylanase Inhibitors and the Presence of Grain‐Associated Xylanases Affect the Activity of Exogenous Xylanases Added to Pelleted Wheat‐Based Feeds

“…The effect of pelleting on GA-XYL activity and on XI activity in wheat is shown in Table II. XIP inhibitor was found to be the most sensitive to heat, because the time needed for 50% reduction of inhibition activity at 100°C was lower than 30 s (Fierens et al 2009). The wheat used in the pelleting trial showed a rather low GA-XYL activity and a rather low XI activity when compared with the ranges found in the previous tests (Table I).…”