Carboxyl group modification significantly altered the kinetic properties of purified carboxymethylcellulase from Aspergillus niger

Siddiqui, Khawar Sohail; Saqib, Abdul Aala Najmus; Rashid, Mohammad Hamid; Rajoka, Muhammad Ibrahim

doi:10.1016/s0141-0229(00)00254-4

Cited by 49 publications

(49 citation statements)

References 26 publications

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“…Thermodynamic values were calculated from kinetic data by plotting activity as a function of temperature (ln units milligram Ϫ1 versus 1/T) according to the Arrhenius equation using Origin Software. Activation energy (E a ) of starch hydrolysis was determined from the slopes of the Arrhenius plots, and thermodynamic parameters of activation (#) were determined using the transition state theory (15,33,34) using the following equations: ). Protein electrophoresis.…”

Section: Enzyme Kinetics and Thermodynamicsmentioning

confidence: 99%

Role of Disulfide Bridges in the Activity and Stability of a Cold-Active α-Amylase

et al. 2005

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The cold-adapted ␣-amylase from Pseudoalteromonas haloplanktis unfolds reversibly and cooperatively according to a two-state mechanism at 30°C and unfolds reversibly and sequentially with two transitions at temperatures below 12°C. To examine the role of the four disulfide bridges in activity and conformational stability of the enzyme, the eight cysteine residues were reduced with ␤-mercaptoethanol or chemically modified using iodoacetamide or iodoacetic acid. Matrix-assisted laser desorption-time of flight mass spectrometry analysis confirmed that all of the cysteines were modified. The iodoacetamide-modified enzyme reversibly folded/unfolded and retained approximately one-third of its activity. Removal of all disulfide bonds resulted in stabilization of the least stable region of the enzyme (including the active site), with a concomitant decrease in activity (increase in activation enthalpy). Disulfide bond removal had a greater impact on enzyme activity than on stability (particularly the active-site region). The functional role of the disulfide bridges appears to be to prevent the active site from developing ionic interactions. Overall, the study demonstrated that none of the four disulfide bonds are important in stabilizing the native structure of enzyme, and instead, they appear to promote a localized destabilization to preserve activity.

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Section: Enzyme Kinetics and Thermodynamicsmentioning

confidence: 99%

Role of Disulfide Bridges in the Activity and Stability of a Cold-Active α-Amylase

et al. 2005

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“…The reducing sugars were determined by adding 3 mL of DNS reagent and the reaction mixture was boiled in a water bath for 10 min, cooled on ice and absorbance was measured at 550 nm. Glucose (50-400 lg) was used to prepare standard curve [41].…”

Section: Protein Estimationmentioning

confidence: 99%

“…The harvested crude enzyme was subjected to five-step purification procedure comprising of fractional precipitation by ammonium sulphate, Hiload anion exchange, Hydrophobic interaction, Mono-Q anion-exchange and Gel filtration chromatography on fast protein liquid chromatography (FPLC) system [26,30,41].…”

Section: Purification Of Cmcasementioning

confidence: 99%

Kinetics and thermodynamics of a novel endoglucanase (CMCase) from Gymnoascella citrina produced under solid-state condition

Jabbar¹,

Rashid

Javed

et al. 2008

J Ind Microbiol Biotechnol

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Gymnoascella citrina produced two isoforms of endoglucanases (CMCase-I and -capital I, Ukrainiancapital I, Ukrainian) under solid-state condition. Purified CMCase-I was novel because it was apparently holoenzyme in nature. The enzyme was monomeric as its native and subunit mass were almost the same, i.e., 43 and 42 kDa, respectively. Ea for carboxymethylcellulose (CMC) hydrolysis was 36.2 kJ mol(-1). The enzyme was stable over a pH range of 3.5-6.5, while temperature optimum was 55 degrees C. Vmax, Km and k (cat )for CMC hydrolysis were 39 U mg(-1) protein, 6.25 mg CMC mL(-1) and 27.5 s(-1), respectively. The pKa1 and pKa2 of ionizable groups of active site were 2.8 and 7.4, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: DeltaH*=33.5 kJ mol(-1), DeltaG*=70.42 kJ mol(-1) and DeltaS*=-114.37 J mol(-1) K(-1). The removal of metals resulted into complete loss of enzymatic activity and was completely recovered in the presence of 1 mM Mn2+, whereas inhibition initiated at 5 mM. The other metals like Ca2+, Zn2+ and K1+ showed no inhibition up to 7 mM, Co2+ completely inhibited the activity, while Mg2+ could not recover the initial activity up to 7 mM. So we are reporting for the first time, kinetics and thermodynamics of CMCase-Iota from G. citrina.

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“…Cellulolytic enzymes also play an important role in natural biodegradation processes in which plant lignocellulosic materials are efficiently degraded (Peciulyte, 2007). Cellulase is multiunit enzyme composed of several enzymes with numerous isozymes (Siddiqui et al, 2000). It comprises three classes of soluble extra cellular enzyme: 1, 4-β-endoglucanase, 1, 4-β exo-glucanase, and β-glucosidase or cellobiase (Siddiqui et al, 2000, Nishida et al, 2007.…”

Section: Introductionmentioning

confidence: 99%

“…Cellulase is multiunit enzyme composed of several enzymes with numerous isozymes (Siddiqui et al, 2000). It comprises three classes of soluble extra cellular enzyme: 1, 4-β-endoglucanase, 1, 4-β exo-glucanase, and β-glucosidase or cellobiase (Siddiqui et al, 2000, Nishida et al, 2007. Endoglucanase hydrolysis internal beta -1,4-glucan chain of glucose, Exo-glucanase remove cellulobiose from the non-reducing end of cello-oligosaccharide, cellobiase hydrolysis cellulobiose to yield two molecules of glucose which deplete the depolymerization of cellulose.…”

Section: Introductionmentioning

confidence: 99%

Isolation and characterization of efficient cellulolytic fungi from degraded wood and industrial samples

Bekele¹,

Abena²,

Habteyohannes³

et al. 2015

Afr. J. Biotechnol.

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Cellulose is the most abundant biopolymer and renewable natural product in the biosphere. Cellulose degrading fungal strains play an important role in recycling of cellulosic materials. They have immense advantage in various industries to hydrolyze cellulosic substrates for production of various products. This study was thus aimed to isolate and characterize efficient cellulose degrading fungi from their common natural habitats. Decaying Acacia wood and industrial water effluent samples were used for isolation and screening of cellulolytic fungi. Both samples were serially diluted and cultured on cellulose basal medium (CBM) supplemented with 30 mg/L chloramphenicol as bactericidal agent. Cellulose degrading fungal isolates were selected based on their hydrolyzed zone after congo red dye stain. Among 13 initial isolates, four isolates (C, E, G, and H) were finally screened as the most efficient fungal isolates representing only degraded Acacia tree. These isolates were confirmed as Penicillium species (C), Apergillus terrus (G), Alternaria species (H) and Apergillus species (E). From this study, the decaying Acacia sample was found to be the best source for cellulolytic fungi than that of wastewater sample. Out of these isolates, the maximum zone of hydrolysis (51.33±1.53 mm) was obtained for 'isolate E', whereas the minimum zone of clearance (26.67±1.53 mm) was recorded for penicillium species. This study indicates the existence of potential cellulolytic fungal on decayed wood of Acacia. Hence, further molecular aided characterizations of the isolates and their enzymes are of paramount importance for their use for industrial purposes.

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Carboxyl group modification significantly altered the kinetic properties of purified carboxymethylcellulase from Aspergillus niger

Cited by 49 publications

References 26 publications

Role of Disulfide Bridges in the Activity and Stability of a Cold-Active α-Amylase

Role of Disulfide Bridges in the Activity and Stability of a Cold-Active α-Amylase

Kinetics and thermodynamics of a novel endoglucanase (CMCase) from Gymnoascella citrina produced under solid-state condition

Isolation and characterization of efficient cellulolytic fungi from degraded wood and industrial samples

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