Cellobiose hydrolysis by endoglucanase (glucan glucanhydrolase) from Trichoderma reesie: Kinetics and mechanism

Glucanohydrolase from Trichoderma reesei, having a molecular weight of 52,000, was evaluated for kinetic properties with respect to cellobiose. Results from this work include: (1) initial rate studies that show that glucanohydrolase hydrolyzes cellobiose by a competitive mechanism and that the product, glucose, inhibits the enzyme; (2) low-pressure aqueous liquid chromatography that shows that formation of a reversion product, cellobiose, is minor and occurs in detectable amounts only a very high (90mM) cellobiose concentrations; (3) development of an equation based on the mechanism of glucanohydrolase action as determined by initial rate kinetics, which accurately predicts the time course of cellobiose hydrolysis; (4) derivation of an initial rate expression for the combined activity of cellobiase and glucanohydrolase on cellobiose. Based on data in this paper it is shown that the difference in inhibition pattern of the two enzymes could be used for determining the contamination of one enzyme by small quantities of the other.     

Modelling of the enzymatic hydrolysis of cellobiose and cellulose by a complex enzyme mixture of Trichoderma reesei QM 9414

Summary The enzymatic hydrolysis of cellobiose and cellulose by the cell-free culture filtrate of Trichoderma reesei QM 9414 was investigated. The concentrations of cellobiose and glucose were measured as a function of time for different initial concentrations of cellobiose. It was not possible to describe these concentration variations by a model which considers only the cellobiase hydrolysis with competitive and noncompetitive substrate and product inhibition; it is necessary that the endo--1.4-glucanase with competitive product inhibition is also taken into account.The enzymatic hydrolysis of cellulose (Avicel) was described with a mathematical model by using the results of the decomposition of cellobiose by the same enzyme mixture.the identified model parameters are presented. A sensitivity analysis of the parameter was carried out also.     

Cellobiase from Trichoderma viride: purification, properties, kinetics, and mechanism

Three distinct cellobiase components were isolated from a commercial Trichoderma viride cellulase preparation by repeated chromatography on DEAE cellulose eluting by a salt gradient. The purified cellobiase preparations were evaluated for physical properties, kinetics, and mechanism. Results from this work include: 1) development of one step enzyme purification procedure using DEAE-cellulose; 2) isolation of three chromatographically distinct, yet kinetically similar, cellobiase fractions of molecular weight of approximately 76,000; 3) determination of kinetics which shows that cellobiase hydrolyzes cellobiose by a noncompetitive mechanism and that the product, glucose, inhibits the enzyme, and 4) development of an equation, based on the mechanism of cellobiase action, which accurately predicts the time course of cellobiose hydrolysis over an eightfold range of substrate concentration and conversions of up to 90%. Based on the data presented in the paper, it is shown that product inhibition of cellobiase significantly retards the rate of cellobiose hydrolysis.     

Kinetic study of the cellobiase activity of Trichoderma reesei cellulase complex at high substrate concentrations

At high cellobiose concentrations, the cellobiase activity of a Trichoderma reesei cellulase preparation does not follow Michaelis–Menten kinetics and shows substrate inhibition. Several rate equations were fitted to the initial rate-cellobiose concentration data. The best fit is obtained for a rate equation corresponding to partial substrate inhibition of cellobiase. In this case, the K_m, V_max and K_I values obtained are 1.1 mM, 16 IU ml^–1 and 26 mM, respectively.     

Kinetics of cellobiose hydrolysis using cellobiase composites from Ttrichoderma reesei and Aspergillus niger

The enzymatic hydrolysis of cellulose to glucose involves the formation of cellobiose as an intermediate. It has been found necessary(1) to add cellobiase from Aspergillus niger (NOVO) to the cellobiase component of Trichoderma reesei mutant Rut C-30 (Natick) cellulase enzymes in order to obtain after 48 h complete conversion of the cellobiose formed in the enzymatic hydrolysis of biomass. This study of the cellobiase activity of these two enzyme sources was undertaken as a first step in the formation of a kinetic model for cellulose hydrolysis that can be used in process design. In order to cover the full range of cellobiose concentrations, it was necessary to develop separate kinetic parameters for high- and low-concentration ranges of cellobiose for the enzymes from each organism. Competitive glucose inhibition was observed with the enzymes from both organisms. Substrate inhibition was observed only with the A. niger enzymes.     

Kinetics and mathematical model of hydrolysis and transglycosylation catalysed by cellobiase

The kinetics of hydrolysis and transglycosylation reactions catalysed by cellobiase (β-d-glucoside glucohydrolase, EC 3.2.1.21) from Aspergillus foetidus in the cellobiose-d-glucose reaction system have been studied. The formation of transglycosylation products was observed at cellobiose concentrations $\text{>10}{}^{\mathrm{?2}}\text{m}$, whereas at lower substrate concentrations the only reaction product was d-glucose. In the cellobiase-catalysed transglycosylation a (1→6)-β-linkage was formed after the transfer of a d-glucose residue to acceptor molecule. The basic transglycosylation products were isocellotriose and gentiobiose. A small amount of oligosaccharides with a higher degree of polymerization was also formed. The maximum content of transglycosylation products amounted to 25–30% of the total saccharide content in the system at the initial cellobiose concentration (0.1–0.3 m). The processes in the reaction system were inhibited by the substrate and product (d-glucose). A general scheme for cellobiose hydrolysis has been proposed and validated, allowing for the inhibition and transglycosylation effects. Based on this scheme, a mathematical model for cellobiose hydrolysis has been suggested to describe the kinetics of substrate consumption and product (d-glucose) accumulation, as well as the kinetics of formation and consumption of transglycosylation products throughout the course of enzymatic reaction with various initial amounts of cellobiose, starting from low concentrations up to 0.2–0.3 m (7–11% bv weight).     

Some kinetic properties of the β- -glucosidase (cellobiase) in a commercial cellulase product from Penicillium funiculosum and its relevance in the hydrolysis of cellulose

Some kinetic parameters of the β- -glucosidase (cellobiase, β- -glucoside glucohydrolase, EC 3.2.1.21) component of Sturge Enzymes CP cellulase [see 1,4-(1,3;1,4)-β- -glucan 4-glucanohydrolase, EC 3.2.1.4] from Penicillium funiculosum have been determined. The Michaelis constants (K_m) for 4-nitrophenyl β- -glucopyranoside (4NPG) and cellobiose are 0.4 and 2.1 mM, respectively, at pH 4.0 and 50°C. -Glucose is shown to be a competitive inhibitor with inhibitor constants (K_i) of 1.7 mM when 4NPG is the substrate and 1 mM when cellobiose is the substrate. Cellobiose, at high concentrations, exhibits a substrate inhibition effect on the enzyme. -Glucono-1,5-lactone is shown to be a potent inhibitor (K_i = 8 μM; 4NPG as substrate) while -fructose exhibits little inhibition. Cellulose hydrolysis progress curves using Avicel or Solka Floc as substrates and a range of commercial cellulase preparations show that CP cellulase gives the best performance, which can be attributed to the activity of the β- -glucosidase in this preparation in maintaining the cellobiose at low concentrations during cellulose hydrolysis.     

On the mode of action of fungal cellulases

Summary The mode of action of the cellulolytic enzymes of two strong cellulose decomposing fungi, Penicillium oxalicum Curie et Thom and Helminthosporium cyclops Drechsler, was studied. The culture filtrates and enzyme preparations obtained from them showed high cellulase activity and very weak cellobiase activity. The cellulolytic system of both experimental organisms seems to be multicomponent. The cellulase component showed its activity mainly extracellulary and the cellobiase component, mainly intracellulary. It seems, therefore, that during growth of both fungi on a cellulose medium, the extracellular cellulase acts hydrolytically on the cellulose substrate forming cellobiose which is further acted upon by intracellular cellobiase to form glucose. Paper chromatographic assay of the products of the enzymatic reaction sub-stantiated this conclusion.     

Effect of glucose and other sugars on the beta-1,4-glucosidase activity of Thermomonospora fusca

The cell-associated beta-glucosidase activity of Thermomonospora fusca, strain YX, showed both PNPGase and cellobiase activities. The cellobiase activity was found by HPLC assay to have very low product inhibition, whereas the PNPGase activity was more significantly inhibited. Of the various sugars and sugar analogs tested for inhibition of the PNPGase activity, gluconolactone had the greatest effect. The low product inhibition of the cellobiase activity was further demonstrated by the production of glucose syrups to 20% concentration from both cellobiose and swollen cellulose (Avicel). This characteristic is of practical importance in the development of a commercial process for the production of glucose syrups from cellulose. Growth experiments gave further evidence for the probability of separate enzymes for the PNPGase and cellobiase activities.     

Cellulolytic enzymes for the hydrolysis of leached beet cosette

Summary Cellulolytic fungi were isolated from rotting leaves and tested for extra-cellular cellulase activities (CMCase, avicelase, cellobiase and xylanase). The effect of the proportion of the enzyme activities on the rate of degradation of leached beet cosette was observed using a range of supernatant fluids in appropriate combinations. At low cosette concentrations (1.5–3.0 g/l), avicelase and cellobiase were the rate limiting enzymes; avicelase in the initial stages of reaction and cellobiase after 6–8 hours, when cellobiose inhibition becomes important. A ratio of celiobiase to avicelase of approx 2.0 was established as appropriate. At higher substrate concentrations (10 g/l, 40 g/l) the best cellobiase to avicelase ratio was maintained and up to 40% hydrolysis was obtained in the 10 g/l incubation with 10 Uav/l and 20 Ucellob/l. At 100 g/l cosette concentration, substrate inhibition was observed.     

Kinetics of the enzymatic hydrolysis of cellulose: 1. A mathematical model for a batch reactor process

A mathematical model for enzymatic cellulose hydrolysis, based on experimental kinetics of the process catalysed by a cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] preparation from Trichoderma longibrachiatum has been developed. The model takes into account the composition of the cellulase complex, the structural complexity of cellulose, the inhibition by reaction products, the inactivation of enzymes in the course of the enzymatic hydrolysis and describes the kinetics of d-glucose and cellobiose formation from cellulose. The rate of d-glucose formation decelerated through the hydrolysis due to a change in cellulose reactivity and inhibition by the reaction product, d-glucose. The rate of cellobiose formation decelerated due to inhibition by the product, cellobiose, and inactivation of enzymes adsorbed on the cellulose surface. Inactivation of the cellobiose-producing enzymes as a result of their adsorption was found to be reversible. The model satisfactorily predicts the kinetics of d-glucose and cellobiose accumulation in a batch reactor up to 70–80% substrate conversion on changing substrate concentration from 5 to 100 g l^?1and the concentration of the enzymic preparation from 5 to 60 g l^?1.     

Some kinetic properties of the β-d-glucosidase (cellobiase) in a commercial cellulase product from Penicillium funiculosum and its relevance in the hydrolysis of cellulose

Some kinetic parameters of the β-d-glucosidase (cellobiase, β-d-glucoside glucohydrolase, EC 3.2.1.21) component of Sturge Enzymes CP cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] from Penicillium funiculosum have been determined. The Michaelis constants (K_m) for 4-nitrophenyl β-d-glucopyranoside (4NPG) and cellobiose are 0.4 and 2.1 mM, respectively, at pH 4.0 and 50°C. d-Glucose is shown to be a competitive inhibitor with inhibitor constants (K_i) of 1.7 mM when 4NPG is the substrate and 1 mM when cellobiose is the substrate. Cellobiose, at high concentrations, exhibits a substrate inhibition effect on the enzyme. d-Glucono-1,5-lactone is shown to be a potent inhibitor (K_i = 8 μM; 4NPG as substrate) while d-fructose exhibits little inhibition. Cellulose hydrolysis progress curves using Avicel or Solka Floc as substrates and a range of commercial cellulase preparations show that CP cellulase gives the best performance, which can be attributed to the activity of the β-d-glucosidase in this preparation in maintaining the cellobiose at low concentrations during cellulose hydrolysis.     

The inhibition of β-glucosidase activity in Trichoderma reesei C30 cellulase by derivatives and isomers of glucose

The inhibition of β-glucosidase in Trichoderma reesei C30 cellulase by D -glucose, its isomers, and derivatives was studied using cellobiose and ρ-nitrophenyl-β-glucoside (PNPG) as substrates for determining enzyme activity. The enzymatic hydrolysis of both substrates was inhibited competitively by glucose with approximate K_i values of 0.5mM and 8.7mM for cellobiose and PNPG as substrate, respectively. This inhibition by glucose was maximal at pH 4.8, and no inhibition was observed at pH 6.5 and above. The α anomer of glucose inhibited β-glucosidase to a greater extent than did the β form. Compared with D -glucose, L -glucose, D -glucose-6-phosphate, and D -glucose-1-phosphate inhibited the enzyme to a much lesser extent, unlike D -glucose-L -cysteine which was almost as inhibitory as glucose itself when cellobiose was used as substrate. Fructose (2?100mM) was found to be a poor inhibitor of the enzyme. It is suggested that high rates of cellobiose hydrolysis catalyzed by β-glucosidase may be prolonged by converting the reaction product glucose to fructose using a suitable preparation of glucose isomerase.     

Properties of the β-d-glucosidase (cellobiase) from the wood-rotting fungus,Coriolus versicolor

Summary Structural and kinetic parameters of the -d-glucosidase (cellobiase, -d-glucoside glucohydrolase) from Coriolus versicolor have been determined. It is a high molecular weight glycoprotein (300,000 d) composed 10% by weight of protein, 90% by weight of carbohydrate in which glucose is the primary hexose sugar. The K_m for 4-nitrophenyl--d-glucopyranoside (4 NPG) and cellobiose are 0.276 and 2.94 mM respectively at pH 4.5 and 40°. d-Glucose is a competitive inhibitor with a K_i of 1.8 mM with 4 NPG as substrate, and at high concentrations, cellobiose exhibits a substrate inhibition effect on the enzyme, so negating attempts to overcome the competitive inhibition of glucose by increasing the concentration of the substrate.     

固定化纤维二糖酶的研究

黑曲霉 (AspergillusnigerLORRE 0 12 )的孢子中富含纤维二糖酶 ,将这些孢子用海藻酸钙凝胶包埋后 ,可以方便有效地固定纤维二糖酶。固定化后的纤维二糖酶性能稳定 ,半衰期为 38d ,耐热性和适宜的pH范围均比固定化前有所增加 ,其Km 和Vmax值分别为 6 .0 1mmol L和 7.0 6mmol (min·L)。利用固定化纤维二糖酶重复分批酶解10g L的纤维二糖 ,连续 10批的酶解得率均可保持在 97%以上 ;采用连续酶解工艺 ,当稀释率为 0 .4h- 1 ,酶解得率可达 98.5 %。玉米芯经稀酸预处理后 ,其纤维残渣用里氏木霉 (Trichodermareesei)纤维素酶降解 ,酶解得率为6 9.5 % ;通过固定化纤维二糖酶的进一步作用 ,上述水解液中因纤维二糖积累所造成的反馈抑制作用得以消除 ,酶解得率提高到 84.2 % ,还原糖中葡萄糖的比例由 5 3 .6 %升至 89.5 % ,该研究结果在纤维原料酶水解工艺中具有良好的应用前景。     

Isolation and Properties of Cellobiase from Penicillium verruculosum

Cellobiase (-D-glucosidase) with a molecular weight of 100 kDa and pI 5.2 was isolated from the cellulolytic system of Penicillium verruculosum. Kinetic parameters of enzymatic hydrolysis of cellobiose, gentiobiose, sophorose, and synthetic substrates, i. e. methylumbelliferyl and p-nitrophenyl sugar derivatives were determined. Glucose and D-glucose--lactone competitively inhibited cellobiase (K _i0.19 mM and 17 M, respectively). Glucosyl transfer reactions were studied with cellobiose as a single substrate and in the mixture of cellobiose and methylumbelliferyl cellobioside. The product composition was determined in these systems. The ratio of hydrolysis and transfer reaction rates for cellobiose conversion was calculated.     

Enzymatic hydrolysis of cellulose. Regulatory effect of the non-soluble substrate on the effectiveness of the enzymatic reaction

It was shown that one of the cellulase components, i.e. cellobiase, can be adsorbed on cellulose surface with the concomitant decrease of activity (by 10 times and more). The specific activity of the adsorbed cellobiase depends on the enzyme concentration in the adsorption layer and is increased with the increase in the surface concentration of cellobiase. It was found that variations in the amount of non-soluble cellulose and the corresponding changes in cellobiase activity in the system (as a result of the adsorption) can lead to a certain alteration in the shape of the kinetic curves for formation of intermediate cellobiose, which in its turn controls the rate of formation of the end product, i.e. glucose. Thus, the substrate surface causes a regulatory effect on the rate and kinetic mechanism of the enzymatic conversion of cellulose to glucose due to the adsorption effects.     

The nature and mode of action of the cellulolytic component C1 of Trichoderma koningii on native cellulose

1. A purified cellulolytic component C(1) was isolated free from associated activities of the cellulase complex and shown to act as a beta-1,4-glucan cellobiohydrolase on both simple and complex forms of native cellulose. 2. The enzyme releases terminal cellobiose units from cellulose, its extent of action being determined principally by the product and by the nature of the substrate. 3. Component C(x) of the cellulase system is not required for the action of component C(1) (cellobiohydrolase). The enzyme synergizes extensively with cellobiase in extending the hydrolysis of native and of less-complex forms of cellulose to at least 70% with the liberation of glucose. 4. The cellobiohydrolase is relatively unstable, with an optimum at pH5 and a K(m) of 0.05mg/ml. The enzyme is inhibited by its product, from which it is released by cellobiase. 5. Of other compounds tested against the cellobiohydrolase the metal ions Cu(2+), Zn(2+), phenylmercuric and Fe(3+) are increasingly effective inhibitors. Glucose has no action at concentrations found inhibitory with cellobiose. 6. The relationship of the enzyme to the entire cellulase complex is discussed.     

Components of cellulase from the higher termite,Nasutitermes walkeri

The cellulase from the termite Nasutitermes walkeri consists of two enzymes. Each has broad specificity with predominantly one activity. One enzyme is an endo-gb-1,4-glucanase (EC 3.2.1.4) which predominantly cleaves cellulose randomly to glucose, cellobiose and cellotriose. It hydrolyses cellotetraose to cellobiose but will not hydrolyse cellobiose or cellotriose. The second enzyme component is a β-1,4-glucosidase (EC 3.2.1.21) as its major activity is to hydrolyse cellobiose, cellotriose and cellotetraose to glucose; it has some exoglucosidase activity as glucose is the only product produced from cellulose. Its cellobiase activity is inhibited by glucono-δ-lactone.     

A comparative study of hydrolysis and transglycosylation activities of fungal β-glucosidases

β-glucosidases (BGs) from Aspergillus fumigatus, Aspergillus niger, Aspergillus oryzae, Magnaporthe grisea, Neurospora crassa, and Penicillium brasilianum were purified to homogeneity, and investigated for their (simultaneous) hydrolytic and transglycosylation activity in samples with high concentrations of either cellobiose or glucose. The rate of the hydrolytic process (which converts one cellobiose to two glucose molecules) shows a maximum around 10–15 mM cellobiose and decreases with further increase in the concentration of substrate. At the highest investigated concentration (100 mM cellobiose), the hydrolytic activity for the different enzymes ranged from 10% to 55% of the maximum value. This decline in hydrolysis was essentially compensated by increased transglycosylation (which converts two cellobiose to one glucose and one trisaccharide). Hence, it was concluded that the hydrolytic slowdown at high substrate concentrations solely relies on an increased flow through the transglycosylation pathway and not an inhibition that delays the catalytic cycle. Transglycosylation was also detected at high product (glucose) concentrations, but in this case, it was not a major cause for the slowdown in hydrolysis. The experimental data was modeled to obtain kinetic parameters for both hydrolysis and transglycosylation. These parameters were subsequently used in calculations that quantified the negative effects on BG activity of respectively transglycosylation and product inhibition. The kinetic parameters and the mathematical method presented here allow estimation of these effects, and we suggest that this may be useful for the evaluation of BGs for industrial use.