1
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A sustainable approach for cotton bioscouring: reuse of the pectate lyase containing treatment bath. Bioprocess Biosyst Eng 2022; 45:1391-1405. [DOI: 10.1007/s00449-022-02753-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 06/27/2022] [Indexed: 11/27/2022]
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2
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Røjel N, Kari J, Sørensen TH, Borch K, Westh P. pH profiles of cellulases depend on the substrate and architecture of the binding region. Biotechnol Bioeng 2019; 117:382-391. [PMID: 31631319 DOI: 10.1002/bit.27206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 09/09/2019] [Accepted: 10/13/2019] [Indexed: 01/06/2023]
Abstract
Understanding the pH effect of cellulolytic enzymes is of great technological importance. In this study, we have examined the influence of pH on activity and stability for central cellulases (Cel7A, Cel7B, Cel6A from Trichoderma reesei, and Cel7A from Rasamsonia emersonii). We systematically changed pH from 2 to 7, temperature from 20°C to 70°C, and used both soluble (4-nitrophenyl β- d-lactopyranoside [pNPL]) and insoluble (Avicel) substrates at different concentrations. Collective interpretation of these data provided new insights. An unusual tolerance to acidic conditions was observed for both investigated Cel7As, but only on real insoluble cellulose. In contrast, pH profiles on pNPL were bell-shaped with a strong loss of activity both above and below the optimal pH for all four enzymes. On a practical level, these observations call for the caution of the common practice of using soluble substrates for the general characterization of pH effects on cellulase activity. Kinetic modeling of the experimental data suggested that the nucleophile of Cel7A experiences a strong downward shift in pKa upon complexation with an insoluble substrate. This shift was less pronounced for Cel7B, Cel6A, and for Cel7A acting on the soluble substrate, and we hypothesize that these differences are related to the accessibility of water to the binding region of the Michaelis complex.
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Affiliation(s)
- Nanna Røjel
- Department of Science and Environment (INM), Roskilde University, Roskilde, Denmark.,Present address: Department of Biotechnology and Biomedicine, Technical University of Denmark, Building 224, DK-2800, Kgs. Lyngby, Denmark
| | - Jeppe Kari
- Department of Science and Environment (INM), Roskilde University, Roskilde, Denmark.,Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| | | | | | - Peter Westh
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
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3
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Kari J, Christensen SJ, Andersen M, Baiget SS, Borch K, Westh P. A practical approach to steady-state kinetic analysis of cellulases acting on their natural insoluble substrate. Anal Biochem 2019; 586:113411. [PMID: 31520594 DOI: 10.1016/j.ab.2019.113411] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 08/26/2019] [Accepted: 08/28/2019] [Indexed: 10/26/2022]
Abstract
Measurement of steady-state rates (vSS) is straightforward in standard enzymology with soluble substrate, and it has been instrumental for comparative biochemical analyses within this area. For insoluble substrate, however, experimental values of vss remain controversial, and this has strongly limited the amount and quality of comparative analyses for cellulases and other enzymes that act on the surface of an insoluble substrate. In the current work, we have measured progress curves over a wide range of conditions for two cellulases, TrCel6A and TrCel7A from Trichoderma reesei, acting on their natural, insoluble substrate, cellulose. Based on this, we consider practical compromises for the determination of experimental vSS values, and propose a basic protocol that provides representative reaction rates and is experimentally simple so that larger groups of enzymes and conditions can be readily assayed with standard laboratory equipment. We surmise that the suggested experimental approach can be useful in comparative biochemical studies of cellulases; an area that remains poorly developed.
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Affiliation(s)
- Jeppe Kari
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, Building 224, DK-2800, Kgs. Lyngby, Denmark
| | - Stefan Jarl Christensen
- Department of Science and Environment, Roskilde University, Universitetsvej, Build. 28.C, DK-4000, Roskilde, Denmark
| | - Morten Andersen
- Department of Science and Environment, Roskilde University, Universitetsvej, Build. 28.C, DK-4000, Roskilde, Denmark
| | | | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880, Bagsværd, Denmark
| | - Peter Westh
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Søltofts Plads, Building 224, DK-2800, Kgs. Lyngby, Denmark.
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4
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A biochemical comparison of fungal GH6 cellobiohydrolases. Biochem J 2019; 476:2157-2172. [DOI: 10.1042/bcj20190185] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 07/14/2019] [Accepted: 07/16/2019] [Indexed: 02/02/2023]
Abstract
AbstractCellobiohydrolases (CBHs) from glycoside hydrolase family 6 (GH6) make up an important part of the secretome in many cellulolytic fungi. They are also of technical interest, particularly because they are part of the enzyme cocktails that are used for the industrial breakdown of lignocellulosic biomass. Nevertheless, functional studies of GH6 CBHs are scarce and focused on a few model enzymes. To elucidate functional breadth among GH6 CBHs, we conducted a comparative biochemical study of seven GH6 CBHs originating from fungi living in different habitats, in addition to one enzyme variant. The enzyme sequences were investigated by phylogenetic analyses to ensure that they were not closely related phylogenetically. The selected enzymes were all heterologously expressed in Aspergillus oryzae, purified and thoroughly characterized biochemically. This approach allowed direct comparisons of functional data, and the results revealed substantial variability. For example, the adsorption capacity on cellulose spanned two orders of magnitude and kinetic parameters, derived from two independent steady-state methods also varied significantly. While the different functional parameters covered wide ranges, they were not independent since they changed in parallel between two poles. One pole was characterized by strong substrate interactions, high adsorption capacity and low turnover number while the other showed weak substrate interactions, poor adsorption and high turnover. The investigated enzymes essentially defined a continuum between these two opposites, and this scaling of functional parameters raises interesting questions regarding functional plasticity and evolution of GH6 CBHs.
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Schiano-di-Cola C, Røjel N, Jensen K, Kari J, Sørensen TH, Borch K, Westh P. Systematic deletions in the cellobiohydrolase (CBH) Cel7A from the fungus Trichoderma reesei reveal flexible loops critical for CBH activity. J Biol Chem 2018; 294:1807-1815. [PMID: 30538133 DOI: 10.1074/jbc.ra118.006699] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 12/08/2018] [Indexed: 11/06/2022] Open
Abstract
Glycoside hydrolase family 7 (GH7) cellulases are some of the most efficient degraders of cellulose, making them particularly relevant for industries seeking to produce renewable fuels from lignocellulosic biomass. The secretome of the cellulolytic model fungus Trichoderma reesei contains two GH7s, termed TrCel7A and TrCel7B. Despite having high structural and sequence similarities, the two enzymes are functionally quite different. TrCel7A is an exolytic, processive cellobiohydrolase (CBH), with high activity on crystalline cellulose, whereas TrCel7B is an endoglucanase (EG) with a preference for more amorphous cellulose. At the structural level, these functional differences are usually ascribed to the flexible loops that cover the substrate-binding areas. TrCel7A has an extensive tunnel created by eight peripheral loops, and the absence of four of these loops in TrCel7B makes its catalytic domain a more open cleft. To investigate the structure-function relationships of these loops, here we produced and kinetically characterized several variants in which four loops unique to TrCel7A were individually deleted to resemble the arrangement in the TrCel7B structure. Analysis of a range of kinetic parameters consistently indicated that the B2 loop, covering the substrate-binding subsites -3 and -4 in TrCel7A, was a key determinant for the difference in CBH- or EG-like behavior between TrCel7A and TrCel7B. Conversely, the B3 and B4 loops, located closer to the catalytic site in TrCel7A, were less important for these activities. We surmise that these results could be useful both in further mechanistic investigations and for guiding engineering efforts of this industrially important enzyme family.
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Affiliation(s)
- Corinna Schiano-di-Cola
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Nanna Røjel
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Kenneth Jensen
- Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark, and
| | - Jeppe Kari
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Trine Holst Sørensen
- From the Department of Science and Environment, Roskilde University, Universitetsvej 1, Building 28, DK-4000 Roskilde, Denmark
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark, and
| | - Peter Westh
- the Department of Biotechnology and Biomedicine, Technical University of Denmark, Building 224, DK-2800 Kgs. Lyngby, Denmark
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6
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Kari J, Kont R, Borch K, Buskov S, Olsen JP, Cruyz-Bagger N, Väljamäe P, Westh P. Anomeric Selectivity and Product Profile of a Processive Cellulase. Biochemistry 2016; 56:167-178. [PMID: 28026938 DOI: 10.1021/acs.biochem.6b00636] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cellobiohydrolases (CBHs) make up an important group of enzymes for both natural carbon cycling and industrial deconstruction of lignocellulosic biomass. The consecutive hydrolysis of one cellulose strand relies on an intricate pattern of enzyme-substrate interactions in the long, tunnel-shaped binding site of the CBH. In this work, we have investigated the initial complexation mode with cellulose of the most thoroughly studied CBH, Cel7A from Hypocrea jecorina (HjCel7A). We found that HjCel7A predominantly produces glucose when it initiates a processive run on insoluble microcrystalline cellulose, confirming the validity of an even and odd product ratio as an estimate of processivity. Moreover, the glucose released from cellulose was predominantly α-glucose. A link between the initial binding mode of the enzyme and the reducing end configuration was investigated by inhibition studies with the two anomers of cellobiose. A clear preference for β-cellobiose in product binding site +2 was observed for HjCel7A, but not the homologous endoglucanase, HjCe7B. Possible relationships between this anomeric preference in the product site and the prevalence of odd-numbered initial-cut products are discussed, and a correlation between processivity and anomer selectivity is proposed.
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Affiliation(s)
- Jeppe Kari
- Research Unit for Functional Biomaterials, Roskilde University , Roskilde, Denmark
| | - Riin Kont
- Institute of Molecular and Cell Biology, University of Tartu , Tartu, Estonia
| | - Kim Borch
- Novozymes A/S , Krogshøjvej 36, DK-2880 Bagsværd, Denmark
| | - Steen Buskov
- Novozymes A/S , Krogshøjvej 36, DK-2880 Bagsværd, Denmark
| | - Johan Pelck Olsen
- Research Unit for Functional Biomaterials, Roskilde University , Roskilde, Denmark
| | | | - Priit Väljamäe
- Institute of Molecular and Cell Biology, University of Tartu , Tartu, Estonia
| | - Peter Westh
- Research Unit for Functional Biomaterials, Roskilde University , Roskilde, Denmark
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7
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Sørensen TH, Windahl MS, McBrayer B, Kari J, Olsen JP, Borch K, Westh P. Loop variants of the thermophileRasamsonia emersoniiCel7A with improved activity against cellulose. Biotechnol Bioeng 2016; 114:53-62. [DOI: 10.1002/bit.26050] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 07/08/2016] [Accepted: 07/11/2016] [Indexed: 01/09/2023]
Affiliation(s)
- Trine Holst Sørensen
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| | | | | | - Jeppe Kari
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| | - Johan Pelck Olsen
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
| | | | - Peter Westh
- NSM, Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1; Building 28, DK-4000 Roskilde Denmark
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8
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Cruys-Bagger N, Alasepp K, Andersen M, Ottesen J, Borch K, Westh P. Rate of Threading a Cellulose Chain into the Binding Tunnel of a Cellulase. J Phys Chem B 2016; 120:5591-600. [DOI: 10.1021/acs.jpcb.6b01877] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicolaj Cruys-Bagger
- Department
of Science and Environment, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark
- Novozymes A/S, Krogshøjvej
36, DK-2880 Bagsværd, Denmark
| | - Kadri Alasepp
- Department
of Science and Environment, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark
| | - Morten Andersen
- Department
of Science and Environment, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark
| | - Johnny Ottesen
- Department
of Science and Environment, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark
| | - Kim Borch
- Novozymes A/S, Krogshøjvej
36, DK-2880 Bagsværd, Denmark
| | - Peter Westh
- Department
of Science and Environment, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark
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9
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Olsen JP, Alasepp K, Kari J, Cruys-Bagger N, Borch K, Westh P. Mechanism of product inhibition for cellobiohydrolase Cel7A during hydrolysis of insoluble cellulose. Biotechnol Bioeng 2016; 113:1178-86. [DOI: 10.1002/bit.25900] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/23/2015] [Accepted: 11/29/2015] [Indexed: 01/10/2023]
Affiliation(s)
- Johan P. Olsen
- Research Unit for Functional Biomaterials; Roskilde University; NSM, 1 Universitetsvej, Build. 28 DK-4000 Roskilde Denmark
| | - Kadri Alasepp
- Research Unit for Functional Biomaterials; Roskilde University; NSM, 1 Universitetsvej, Build. 28 DK-4000 Roskilde Denmark
| | - Jeppe Kari
- Research Unit for Functional Biomaterials; Roskilde University; NSM, 1 Universitetsvej, Build. 28 DK-4000 Roskilde Denmark
| | - Nicolaj Cruys-Bagger
- Research Unit for Functional Biomaterials; Roskilde University; NSM, 1 Universitetsvej, Build. 28 DK-4000 Roskilde Denmark
- Novozymes A/S; Bagsvaerd Denmark
| | | | - Peter Westh
- Research Unit for Functional Biomaterials; Roskilde University; NSM, 1 Universitetsvej, Build. 28 DK-4000 Roskilde Denmark
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10
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Sørensen TH, Cruys-Bagger N, Windahl MS, Badino SF, Borch K, Westh P. Temperature Effects on Kinetic Parameters and Substrate Affinity of Cel7A Cellobiohydrolases. J Biol Chem 2015; 290:22193-202. [PMID: 26183777 DOI: 10.1074/jbc.m115.658930] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Indexed: 11/06/2022] Open
Abstract
We measured hydrolytic rates of four purified cellulases in small increments of temperature (10-50 °C) and substrate loads (0-100 g/liter) and analyzed the data by a steady state kinetic model that accounts for the processive mechanism. We used wild type cellobiohydrolases (Cel7A) from mesophilic Hypocrea jecorina and thermophilic Rasamsonia emersonii and two variants of these enzymes designed to elucidate the role of the carbohydrate binding module (CBM). We consistently found that the maximal rate increased strongly with temperature, whereas the affinity for the insoluble substrate decreased, and as a result, the effect of temperature depended strongly on the substrate load. Thus, temperature had little or no effect on the hydrolytic rate in dilute substrate suspensions, whereas strong temperature activation (Q10 values up to 2.6) was observed at saturating substrate loads. The CBM had a dual effect on the activity. On one hand, it diminished the tendency of heat-induced desorption, but on the other hand, it had a pronounced negative effect on the maximal rate, which was 2-fold larger in variants without CBM throughout the investigated temperature range. We conclude that although the CBM is beneficial for affinity it slows down the catalytic process. Cel7A from the thermophilic organism was moderately more activated by temperature than the mesophilic analog. This is in accord with general theories on enzyme temperature adaptation and possibly relevant information for the selection of technical cellulases.
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Affiliation(s)
- Trine Holst Sørensen
- From Roskilde University, Nature, Systems, and Models, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and
| | - Nicolaj Cruys-Bagger
- From Roskilde University, Nature, Systems, and Models, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and
| | - Michael Skovbo Windahl
- From Roskilde University, Nature, Systems, and Models, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark
| | - Silke Flindt Badino
- From Roskilde University, Nature, Systems, and Models, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark
| | - Peter Westh
- From Roskilde University, Nature, Systems, and Models, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and
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11
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Sørensen TH, Cruys-Bagger N, Borch K, Westh P. Free Energy Diagram for the Heterogeneous Enzymatic Hydrolysis of Glycosidic Bonds in Cellulose. J Biol Chem 2015; 290:22203-11. [PMID: 26183776 DOI: 10.1074/jbc.m115.659656] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Indexed: 01/25/2023] Open
Abstract
Kinetic and thermodynamic data have been analyzed according to transition state theory and a simplified reaction scheme for the enzymatic hydrolysis of insoluble cellulose. For the cellobiohydrolase Cel7A from Hypocrea jecorina (Trichoderma reesei), we were able to measure or collect relevant values for all stable and activated complexes defined by the reaction scheme and hence propose a free energy diagram for the full heterogeneous process. For other Cel7A enzymes, including variants with and without carbohydrate binding module (CBM), we obtained activation parameters for the association and dissociation of the enzyme-substrate complex. The results showed that the kinetics of enzyme-substrate association (i.e. formation of the Michaelis complex) was almost entirely entropy-controlled and that the activation entropy corresponded approximately to the loss of translational and rotational degrees of freedom of the dissolved enzyme. This implied that the transition state occurred early in the path where the enzyme has lost these degrees of freedom but not yet established extensive contact interactions in the binding tunnel. For dissociation, a similar analysis suggested that the transition state was late in the path where most enzyme-substrate contacts were broken. Activation enthalpies revealed that the rate of dissociation was far more temperature-sensitive than the rates of both association and the inner catalytic cycle. Comparisons of one- and two-domain variants showed that the CBM had no influence on the transition state for association but increased the free energy barrier for dissociation. Hence, the CBM appeared to promote the stability of the complex by delaying dissociation rather than accelerating association.
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Affiliation(s)
- Trine Holst Sørensen
- From Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and
| | - Nicolaj Cruys-Bagger
- From Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880 Bagsværd, Denmark
| | - Peter Westh
- From Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Roskilde, Denmark and
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12
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Colussi F, Sørensen TH, Alasepp K, Kari J, Cruys-Bagger N, Windahl MS, Olsen JP, Borch K, Westh P. Probing substrate interactions in the active tunnel of a catalytically deficient cellobiohydrolase (Cel7). J Biol Chem 2014; 290:2444-54. [PMID: 25477511 DOI: 10.1074/jbc.m114.624163] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellobiohydrolases break down cellulose sequentially by sliding along the crystal surface with a single cellulose strand threaded through the catalytic tunnel of the enzyme. This so-called processive mechanism relies on a complex pattern of enzyme-substrate interactions, which need to be addressed in molecular descriptions of processivity and its driving forces. Here, we have used titration calorimetry to study interactions of cellooligosaccharides (COS) and a catalytically deficient variant (E212Q) of the enzyme Cel7A from Trichoderma reesei. This enzyme has ∼10 glucopyranose subsites in the catalytic tunnel, and using COS ligands with a degree of polymerization (DP) from 2 to 8, different regions of the tunnel could be probed. For COS ligands with a DP of 2-3 the binding constants were around 10(5) m(-1), and for longer ligands (DP 5-8) this value was ∼10(7) m(-1). Within each of these groups we did not find increased affinity as the ligands got longer and potentially filled more subsites. On the contrary, we found a small but consistent affinity loss as DP rose from 6 to 8, particularly at the higher investigated temperatures. Other thermodynamic functions (ΔH, ΔS, and ΔCp) decreased monotonously with both temperature and DP. Combined interpretation of these thermodynamic results and previously published structural data allowed assessment of an affinity profile along the length axis of the active tunnel.
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Affiliation(s)
- Francieli Colussi
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Trine H Sørensen
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Kadri Alasepp
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Jeppe Kari
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Nicolaj Cruys-Bagger
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Michael S Windahl
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and Novozymes A/S, Krogshøjvej 36, DK-2880, Bagsværd, Denmark
| | - Johan P Olsen
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880, Bagsværd, Denmark
| | - Peter Westh
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
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13
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Eibinger M, Ganner T, Bubner P, Rošker S, Kracher D, Haltrich D, Ludwig R, Plank H, Nidetzky B. Cellulose surface degradation by a lytic polysaccharide monooxygenase and its effect on cellulase hydrolytic efficiency. J Biol Chem 2014; 289:35929-38. [PMID: 25361767 PMCID: PMC4276861 DOI: 10.1074/jbc.m114.602227] [Citation(s) in RCA: 180] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Lytic polysaccharide monooxygenase (LPMO) represents a unique principle of oxidative degradation of recalcitrant insoluble polysaccharides. Used in combination with hydrolytic enzymes, LPMO appears to constitute a significant factor of the efficiency of enzymatic biomass depolymerization. LPMO activity on different cellulose substrates has been shown from the slow release of oxidized oligosaccharides into solution, but an immediate and direct demonstration of the enzyme action on the cellulose surface is lacking. Specificity of LPMO for degrading ordered crystalline and unordered amorphous cellulose material of the substrate surface is also unknown. We show by fluorescence dye adsorption analyzed with confocal laser scanning microscopy that a LPMO (from Neurospora crassa) introduces carboxyl groups primarily in surface-exposed crystalline areas of the cellulosic substrate. Using time-resolved in situ atomic force microscopy we further demonstrate that cellulose nano-fibrils exposed on the surface are degraded into shorter and thinner insoluble fragments. Also using atomic force microscopy, we show that prior action of LPMO enables cellulases to attack otherwise highly resistant crystalline substrate areas and that it promotes an overall faster and more complete surface degradation. Overall, this study reveals key characteristics of LPMO action on the cellulose surface and suggests the effects of substrate morphology on the synergy between LPMO and hydrolytic enzymes in cellulose depolymerization.
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Affiliation(s)
- Manuel Eibinger
- From the Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria
| | - Thomas Ganner
- Institute of Electron Microscopy and Nanoanalysis and
| | - Patricia Bubner
- From the Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria
| | | | - Daniel Kracher
- Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and
| | - Dietmar Haltrich
- Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and
| | - Roland Ludwig
- Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and
| | - Harald Plank
- Institute of Electron Microscopy and Nanoanalysis and Graz Centre for Electron Microscopy, Steyrergasse 17, A-8010 Graz, Austria,
| | - Bernd Nidetzky
- From the Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria, Austrian Centre of Industrial Biotechnology, Petersgasse 14, A-8010 Graz, Austria
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Kari J, Olsen J, Borch K, Cruys-Bagger N, Jensen K, Westh P. Kinetics of cellobiohydrolase (Cel7A) variants with lowered substrate affinity. J Biol Chem 2014; 289:32459-68. [PMID: 25271162 DOI: 10.1074/jbc.m114.604264] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellobiohydrolases are exo-active glycosyl hydrolases that processively convert cellulose to soluble sugars, typically cellobiose. They effectively break down crystalline cellulose and make up a major component in industrial enzyme mixtures used for deconstruction of lignocellulosic biomass. Identification of the rate-limiting step for cellobiohydrolases remains controversial, and recent reports have alternately suggested either association (on-rate) or dissociation (off-rate) as the overall bottleneck. Obviously, this uncertainty hampers both fundamental mechanistic understanding and rational design of enzymes with improved industrial applicability. To elucidate the role of on- and off-rates, respectively, on the overall kinetics, we have expressed a variant in which a tryptophan residue (Trp-38) in the middle of the active tunnel has been replaced with an alanine. This mutation weakens complex formation, and the population of substrate-bound W38A was only about half of the wild type. Nevertheless, the maximal, steady-state rate was twice as high for the variant enzyme. It is argued that these opposite effects on binding and activity can be reconciled if the rate-limiting step is after the catalysis (i.e. in the dissociation process).
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Affiliation(s)
- Jeppe Kari
- From Department of Science, Systems and Models, Research Unit for Functional Biomaterials, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark and
| | - Johan Olsen
- From Department of Science, Systems and Models, Research Unit for Functional Biomaterials, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark and
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, Bagsværd DK-2880, Denmark
| | - Nicolaj Cruys-Bagger
- From Department of Science, Systems and Models, Research Unit for Functional Biomaterials, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark and
| | - Kenneth Jensen
- Novozymes A/S, Krogshøjvej 36, Bagsværd DK-2880, Denmark
| | - Peter Westh
- From Department of Science, Systems and Models, Research Unit for Functional Biomaterials, Roskilde University, 1 Universitetsvej, DK-4000 Roskilde, Denmark and
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