Impact of an N-terminal extension on the stability and activity of the GH11 xylanase from Thermobacillus xylanilyticus.
To understand structure-function relationships in the N-terminal region of GH11 xylanases, the 17 N-terminal amino acids of the GH11 xylanase from Neocallimastix patriciarum (Np-Xyn) have been grafted onto the N-terminal extremity of the untypically short GH11 xylanase from Thermobacillus xylanilyticus (Tx-Xyn), creating a hybrid enzyme denoted NTfus. The hybrid xylanase displayed properties (pH and temperature optima) similar to those of the parental enzyme, although thermostability was lowered, with the Tm value, being reduced by 5°C. Kinetic assays using oNP-Xylo-oligosaccharides (DP2 and 3) indicated that the N-extension did not procure more extensive substrate binding, even when further mutagenesis was performed to promote this. However, these experiments confirmed weak subsite -3 for both NTfus and the parental enzyme. The catalytic efficiency of NTfus was shown to be 17% higher than that of the parental enzyme on low viscosity wheat arabinoxylan and trials using milled wheat straw as the substrate revealed that NTfus released more substituted oligosaccharide products (Xyl/Ara=8.97±0.13 compared to Xyl/Ara=9.70±0.21 for the parental enzyme), suggesting that the hybrid enzyme possesses wider substrate selectivity. Combining either the parental enzyme or NTfus with the cellulolytic cocktail Accellerase 1500 boosted the impact of the latter on wheat straw, procuring yields of solubilized xylose and glucose of 23 and 24% of theoretical yield, respectively, thus underlining the benefits of added xylanase activity when using this cellulase cocktail. Overall, in view of the results obtained for NTfus, we propose that the N-terminal extension leads to the modification of a putative secondary substrate binding site, a hypothesis that is highly consistent with previous data.
Université de Toulouse, INSA,UPS,INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France.
Letian
L
Song
Université de Toulouse, INSA,UPS,INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France.
Claire
C
Dumon
Université de Toulouse, INSA,UPS,INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France; CNRS, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, France.
Béatrice
B
Siguier
Université de Toulouse, INSA,UPS,INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France.
Isabelle
I
André
National Research Center "Kurchatov Institute", B.P. Konstantinov Petersburg Nuclear Physics Institute, Gatchina, 188350 St. Petersburg, Russia.
Elena
E
Eneyskaya
National Research Center "Kurchatov Institute", B.P. Konstantinov Petersburg Nuclear Physics Institute, Gatchina, 188350 St. Petersburg, Russia.
Anna
A
Kulminskaya
Université de Toulouse, INSA,UPS,INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France.
Sophie
S
Bozonnet
Université de Toulouse, INSA,UPS,INP, LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France; INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France; CNRS, UMR5504, F-31400 Toulouse, France. Electronic address: michael.odonohue@insa-toulouse.fr.
Michael Joseph
MJ
O'Donohue
D000595:Amino Acid Sequence; D001407:Bacillus / Q000737:chemistry / Q000145:classification / Q000201:enzymology*; D020134:Catalytic Domain; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020088:Neocallimastix / Q000145:classification / Q000235:genetics*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D013696:Temperature
D005656:Fungal Proteins; D011994:Recombinant Proteins; D043364:Endo-1,4-beta Xylanases
GH11 xylanase; Hybrid enzyme; N-terminal region; Secondary binding site; −3 subsite mapping