The predominant molecular state of bound enzyme determines the strength and type of product inhibition in the hydrolysis of recalcitrant polysaccharides by processive enzymes

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Human Chitotriosidase Is an Endo-Processive Enzyme

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MOESM1 of When substrate inhibits and inhibitor activates: implications of β-glucosidases

Additional file 1: Figure S1. Effect of inhibitor to an enzyme exerting the nonproductive binding of substrate. Figure S2. Effects of inhibitor to enzymes exerting the nonproductive binding of substrate and transglycosylation to inhibitor-formation of the second product. Figure S3. Effects of inhibitor to enzymes exerting the nonproductive binding of substrate and transglycosylation to inhibitor-formation of the transglycosylation product. Figure S4. Effects of inhibitor to enzymes exerting the transglycosylation to inhibitor that binds to the “transglycosylation-binding-site”

Estimation of Gap Fraction and Foliage Clumping in Forest Canopies

The gap fractions of three mature hemi-boreal forest stands in Estonia were estimated using the LAI-2000 plant canopy analyzer ( LI-COR Biosciences, Lincoln, NE, USA), the TRAC instrument (Edgewall, Miami, FL, USA), Cajanus’ tube, hemispherical photos, as well as terrestrial (TLS) and airborne (ALS) laser scanners. ALS measurements with an 8-year interval confirmed that changes in the structure of mature forest stands are slow, and that measurements in the same season of different years should be well comparable. Gap fraction estimates varied considerably depending on the instruments and methods used. None of the methods considered for the estimation of gap fraction of forest canopies proved superior to others. The increasing spatial resolution of new ALS devices allows the canopy structure to be analyzed in more detail than was possible before. The high vertical resolution of point clouds improves the possibility of estimating the stand height, crown length, and clumping of foliage in the canopy. The clumping/regularity of the foliage in a forest canopy is correlated with tree height, crown length, and basal area. The method suggested herein for the estimation of foliage clumping allows the leaf area estimates of forest canopies to be improved

Kinetics of H2O2-driven degradation of chitin by a bacterial lytic polysaccharide monooxygenase

International audienceLytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds in recalcitrant polysaccharides, such as cellulose and chitin, and are of interest in biotechnological utilization of these abundant biomaterials. It has recently been shown that LPMOs can use H2O2, instead of O-2, as a cosubstrate. This peroxygenase-like reaction by a monocopper enzyme is unprecedented in nature and opens new avenues in chemistry and enzymology. Here, we provide the first detailed kinetic characterization of chitin degradation by the bacterial LPMO chitin-binding protein CBP21 using H2O2 as cosubstrate. The use of C-14-labeled chitin provided convenient and sensitive detection of the released soluble products, which enabled detailed kinetic measurements. The k(cat) for chitin oxidation found here (5.6 s(-1)) is more than an order of magnitude higher than previously reported (apparent) rate constants for reactions containing O-2 but no added H2O2. The k(cat)/K-m for H2O2-driven degradation of chitin was on the order of 10(6) m(-1) s(-1), indicating that LPMOs have catalytic efficiencies similar to those of peroxygenases. Of note, H2O2 also inactivated CBP21, but the second-order rate constant for inactivation was about 3 orders of magnitude lower than that for catalysis. In light of the observed CBP21 inactivation at higher H2O2 levels, we conclude that controlled generation of H(2)O(2)in situ seems most optimal for fueling LPMO-catalyzed oxidation of polysaccharides

NAG₂ inhibition of HCHT.

<p>(A) Activity of HCHT on MU-NAG₂ substrate as a function of substrate concentration. (B) NAG₂ inhibition of HCHT on MU-NAG₂ substrate measured at 3 different substrate concentrations—0.5 μM, 5 μM or 50 μM. (C) NAG₂ inhibition of HCHT on ¹⁴C-CNW substrate (1.0 g/L). <i>v</i>_i and <i>v</i>_{i = 0} stand for the rates measured in the presence and absence of inhibitor, respectively. Error bars show standard deviations and are from three independent experiments.</p

SDS-PAGE analysis of purified chitinases.

<p>4–6 μg purified HCHT 50 kDa and 39 kDa isoforms and <i>S</i>. <i>marcescens</i> chitinases <i>Sm</i>ChiA, <i>Sm</i>ChiB and <i>Sm</i>ChiC were loaded and the gel was stained with Coomassie Brilliant Blue G-250.</p

Endo-probability and processivities measured on α-chitin.

<p>Endo-probability and processivities measured on α-chitin.</p

Progress curves of AA-CNW hydrolysis.

<p>(A) AA-CNWs (1 mg/mL) were hydrolysed with HCHT50, HCHT39, <i>Sm</i>ChiA, <i>Sm</i>ChiB or <i>Sm</i>ChiC at 37°C. The release of AA-labelled sugars and total soluble reducing ends were measured at defined time points (5, 10, 20, 40 and 60 min). Error bars show standard deviations and are from three independent experiments. (B) Progress curves at different concentrations of HCHT39.</p