Partial Characterization of the Active Site of Carrot Poly(galacturonate) Hydrolase and Degradation of Oligo(D-galactosiduronates)

1995 ◽  
Vol 60 (2) ◽  
pp. 328-338 ◽  
Author(s):  
Kveta Heinrichová ◽  
Július Heinrich ◽  
Mária Dzúrová
Keyword(s):  
Active Center ◽  
Hydrolytic Cleavage ◽  
Catalytic Hydrolysis ◽  
Optimal Conditions ◽  
Polymerization Degree ◽  
Enzyme Degradation ◽  
Good Accord ◽  
Michaelis Constants ◽  
Hydrolysis Of

The dimension and arrangement of the active center in carrot poly(1→4-α-D-galacturonide)galacturonohydrolase (E.C.3.2.1.67) is studied. Molecular activities k0 and parameters k0/Km were calculated from the experimentally determined Michaelis constants Km and maximum rates of catalytic hydrolysis of linear oligo(D-galactosiduronates) (polymerization degree n = 2 to 7) at pH 5.0 and 30 °C. From the dependence of log k0 and log k0/Km on n we derived that the active center consists of six subsites, the catalytic site being situated between the first and second subsite. In accord with the theory of Hiromi [Hiromi K.: Biochem. Biophys. Res. Commun. 40, 1 (1970)], the kinetic data were used for calculation of affinities (Ai) of the third (A3) to the sixth (A6) subsite. Two possible models were studied for the action of carrot poly(galacturonate)hydrolase which catalyzes the gradual terminal hydrolytic cleavage of oligo(D-galactosiduronates) from the non-reducing end of the molecule. The distribution of products in monomolecular hydrolysis of penta(D-galactosiduronate) under optimal conditions (pH and temperature) indicates a multi-chain enzymatic attack with predominant single collision. The kinetic results of the enzyme degradation are in good accord with the above-mentioned assumption.

Mode of Action and Partial Purification of the Active Centre of exo-Poly-α-D-galacturonosidase from Selenomonas ruminantium

1993 ◽  
Vol 58 (3) ◽  
pp. 681-692
Author(s):  
Kveta Heinrichová ◽  
Július Heinrich ◽  
Mária Dzúrová ◽  
Alexander Ziolecki
Keyword(s):  
Mode Of Action ◽  
Kinetic Data ◽  
Degree Of Polymerization ◽  
Partial Purification ◽  
Catalytic Hydrolysis ◽  
Product Analysis ◽  
Active Centre ◽  
Selenomonas Ruminantium ◽  
Michaelis Constants ◽  
Hydrolysis Of

In the presented paper are summarized results of the study of the mode of action, dimensions and arrangement of the active centre of the exo-poly-α-D-galacturonosidase, (poly(1,4-α-D-galactosiduronate) digalacturonohydrolase, E.C. 3.2.1.82) produced by the bacteria Selenomonas ruminantium. With this aim we determined experimentally values of Michaelis constants and limiting rates for the catalytic hydrolysis of linear oligo(D-galactosiduronates) of the degree of polymeration in the range of 3 to 8, at pH 7.0 and the temperature 30 °C. We calculated molecular activities k0 and parameters k0/Km from these values. From the dependence of logk0 and logk0/Km on the degree of polymerization five subsites of the active centre were determined, with the catalytic site being situated between the second and third one. Kinetic data were used for the calculation of the affinities of the fourth and fifth subsites A4 and A5 in accordance with the theory of Hiromi. Product analysis of non-labelled oligo(D-galactosiduronates) and compounds labelled with [1-3H] at the reducing end anabled to ascertain approximately the value for the first subsite A1 of the active centre and to study the mode of action of the exo-poly-α-D-galacturonosidase from Selenomonas ruminantium.

Study on the Synthesis of Ethylene Glycol by Catalytic Hydrolyze of Ethylene Carbonate

2014 ◽  
Vol 989-994 ◽  
pp. 79-82
Author(s):  
Min Zhang
Keyword(s):  
Reaction Time ◽  
Ethylene Glycol ◽  
Influencing Factors ◽  
Reaction Temperature ◽  
Mass Fraction ◽  
Ethylene Carbonate ◽  
Catalytic Hydrolysis ◽  
Optimal Conditions ◽  
Reaction Products ◽  
Hydrolysis Of

The process for ethylene glycol (EG) by catalytic hydrolysis of ethylene carbonate (EC) was studied. The influencing factors of the reaction products were studied which include the reaction temperature, the mole ratio of H2O to EC, the mass fraction of the catalyst and the reaction time. The optimal conditions were identified as follows: the reaction temperature is 140-145°C, n (H2O) :n (EC) = 2.0-2.5 : 1, the catalyst of Al2O3is about 2.0wt%, the reaction time is about two hours. Under the above conditions, EC can be completely hydrolyzed and the selectivity of EG is above 98%.

THE INFLUENCE OF HYDROGEN ION CONCENTRATION ON THE MYOSIN-CATALYZED HYDROLYSIS OF ADENOSINE TRIPHOSPHATE

1961 ◽  
Vol 39 (7) ◽  
pp. 1444-1453 ◽  
Author(s):  
Gérard E. Pelletier ◽  
Ludovic Ouellet
Keyword(s):  
Experimental Data ◽  
Potassium Chloride ◽  
Active Center ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Kcal Mole ◽  
Hydrogen Ion Concentration ◽  
Michaelis Constants ◽  
Hydrolysis Of ◽  
Ionizable Groups

The Michaelis constants for the system myosin–ATP have been measured at 5 °C and 15 °C from pH 7.0 to pH 10.5, in the presence of 0.4 M potassium chloride and 0.005 M calcium chloride. The experimental data point to the presence, in the active center, of two ionizable groups, with experimental acid pK of 7.35 and 8.6 respectively at 15 °C. The apparent heats of ionization of these groups are about 9 kcal/mole for the first one and close to zero for the second. These data are interpreted as indication of the presence in the active center of myosin of a histidyl and a sulphydryl residue. A mechanism is proposed for the hydrolysis of ATP in the presence of myosin.

Multi-chain action of exo-D-galacturonanase from carrot

1983 ◽  
Vol 48 (12) ◽  
pp. 3579-3588
Author(s):  
Kveta Heinrichová ◽  
Jana Perečková
Keyword(s):  
Optimal Condition ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Hydrolytic Cleavage ◽  
Chain Mechanism ◽  
Modes Of Action ◽  
Enzyme Degradation ◽  
Good Agreement

Two possible modes of action of exo-D-galacturonanase from carrot (E.C. 3.2.1.67) were investigated; this enzyme catalyses the sequential hydrolytic cleavage of pectants and oligogalacturonans by a terminal action from the nonreducing end of the molecule. The experiments indicate that the investigated exo-D-galacturonanase degrades these substrates by a predominantly multi-chain mechanism. Distribution of degradation products of oligomeric substrates (hexa- and pentagalacturonide) under an optimal condition for the action of the enzyme (pH and temperature) indicates that a multi-chain enzyme attack with a prevalent simple collision is involved. Results of the enzyme degradation kinetics are in a good agreement with the above-mentioned presumption.

scholarly journals Pretreatment of Switchgrass for Production of Glucose via Sulfonic Acid-Impregnated Activated Carbon

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 504
Author(s):  
Yane Ansanay ◽  
Praveen Kolar ◽  
Ratna Sharma-Shivappa ◽  
Jay Cheng ◽  
Consuelo Arellano
Keyword(s):  
Activated Carbon ◽  
Sulfonic Acid ◽  
Solid Acid ◽  
Methanesulfonic Acid ◽  
Biofuel Production ◽  
Acid Catalysts ◽  
Effects Of Temperature ◽  
Carbon Catalysts ◽  
Hydrolysis Of

In the present research, activated carbon-supported sulfonic acid catalysts were synthesized and tested as pretreatment agents for the conversion of switchgrass into glucose. The catalysts were synthesized by reacting sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid with activated carbon. The characterization of catalysts suggested an increase in surface acidities, while surface area and pore volumes decreased because of sulfonation. Batch experiments were performed in 125 mL serum bottles to investigate the effects of temperature (30, 60, and 90 °C), reaction time (90 and 120 min) on the yields of glucose. Enzymatic hydrolysis of pretreated switchgrass using Ctec2 yielded up to 57.13% glucose. Durability tests indicated that sulfonic solid-impregnated carbon catalysts were able to maintain activity even after three cycles. From the results obtained, the solid acid catalysts appear to serve as effective pretreatment agents and can potentially reduce the use of conventional liquid acids and bases in biomass-into-biofuel production.

scholarly journals Characterization of the Active Center of Thioredoxin Reductase

1967 ◽  
Vol 242 (22) ◽  
pp. 5232-5236 ◽  
Author(s):  
Giuliana Zanetti ◽  
Charles H. Williams
Keyword(s):  
Active Center ◽  
Thioredoxin Reductase
Sign in / Sign up

Export Citation Format

Share Document