Dissociation of acetyl derivatives of pectic acid and intramolecular binding of calcium ions to those substances

1978 ◽  
Vol 43 (7) ◽  
pp. 1709-1719 ◽  
Author(s):  
Rudolf Kohn ◽  
Anna Malovíková
Keyword(s):  
Calcium Ions ◽  
Pectic Acid ◽  
Derivatives Of

Binding of calcium ions to 2,3-dicarboxy derivatives of pectic acid

1986 ◽  
Vol 51 (10) ◽  
pp. 2259-2270 ◽  
Author(s):  
Anna Malovíková ◽  
Rudolf Kohn
Keyword(s):  
Activity Coefficient ◽  
Calcium Ions ◽  
High Selectivity ◽  
Carboxyl Groups ◽  
Free Enthalpy ◽  
Pectic Acid ◽  
Considerable Degradation ◽  
Oxidation Degradation ◽  
Derivatives Of ◽  
Low Activity

Using a two-step oxidation of pectic acid (85% of D-galacturonan in the preparation) a series of 2,3-dicarboxy derivatives (Na+ form) was prepared containing 4.2 to 8.5 mmol of carboxyl groups per gram (COOH g-1). After the centrifugation of the diluted suspensions of the Ca-salts of these polyacids the activity of the calcium counterions (aCa2+) was determined using the metallochromic indicator (tetramethylmurexide) and the activity coefficient γCa2+ was calculated. Using potentiometric titrations of polyacids with potassium and calcium hydroxides the decrease in electrostatic free enthalpy, Δ(Gel/N)KCa, of the cation exchange Ca2+ → 2 K+ was determined. In the course of the oxidation, degradation of the macromolecules took place, characterized by the limit viscosity number [η]. In spite of the considerable degradation, preparations with higher oxidation degrees display a high selectivity in the exchange of cations Ca2+ → 2 K+, similar to that determined recently by us in 2,3-dicarboxy derivatives of starch and amylose. The strong binding of Ca2+ ions to the investigated substances is also documented by very low activity coefficient values, γCa2+, ranging from 0.057 to 0.037.

Intramolecular binding of calcium ions to L-guluronan and D-galacturonan

1981 ◽  
Vol 46 (7) ◽  
pp. 1701-1707 ◽  
Author(s):  
Rudolf Kohn ◽  
Anna Malovíková
Keyword(s):  
Activity Coefficients ◽  
Calcium Ions ◽  
Uronic Acid ◽  
Total Activity ◽  
Polymeric Chain ◽  
Polymerization Degree ◽  
Pectic Acid ◽  
Calcium Salts ◽  
Macromolecule Chain ◽  
Derivatives Of

The values of activity coefficients γCa2+, determined earlier in solutions of calcium oligoguluronates and oligogalacturonates of various polymerization degree n, were interpreted. Values γCa2+ corresponding to an intramolecular Ca2+ bond to a polymeric chain of L-guluronan and D-galacturonan were obtained by extrapolation of functions γCa2+ = f(1/n) and γCa2+ = f((n-2)/n) to lim n → ##h. The γCa2+ values were compared with those determined in solutions of calcium salts of O-acetyl derivatives of pectic acid and D-mannuronan. In molecular disperse solutions the Ca2+ ions are bound to L-guluronan and D-galacturonan by an electrostatic bond. The course of the above-mentioned functions leads to the conclusion that both terminal uronic acid units in polyuronates under study bind Ca2+ ions less firmly than do the inner units in the macromolecule chain. The linear course of the function γCa2+ = f((n-2)/n) for L-guluronan proves the additivity of contribution of the terminal and inner uronic acid units to the total activity of Ca2+ counterions bound to L-guluronan.

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

scholarly journals Derivatives of Pectic Acid as Models of Proteins

Nature ◽  
1947 ◽  
Vol 159 (4052) ◽  
pp. 882-882 ◽  
Author(s):  
H. DEUEL ◽  
H. NEUKOM
Keyword(s):  
Pectic Acid ◽  
Derivatives Of

Activation of Prothrombin

1956 ◽  
Vol 186 (2) ◽  
pp. 343-349 ◽  
Author(s):  
John A. Penner ◽  
Walter H. Seegers
Keyword(s):  
Calcium Ions ◽  
Platelet Factor ◽  
Derivatives Of ◽  
Prothrombin Activation

In the activation of a prothrombin solution, only part of the prothrombin becomes biothrombin, some becomes autoprothrombin I and some becomes autoprothrombin II. Thrombin-thrombin is also obtained, and perhaps other derivatives of prothrombin are formed. Prothrombin thus has multiple potentialities and these can be developed in diverse ways. Ac-globulin, calcium ions and platelet factor 3 can be used to obtain autoprothrombin I. Thrombin and Ac-globulin transforms prothrombin to autoprothrombin II, while platelet factor 3 or calcium ions tend to inhibit the transformation. Since calcium ions and platelet factor 3 also function as activators in one of the prothrombin to biothrombin reactions they are either activators or inhibitors of prothrombin activation depending upon the specified conditions.

The selective cleavage of permethylated glycopyranosiduronic acid linkages by oxidative decarboxylation with lead tetraacetate

1981 ◽  
Vol 59 (6) ◽  
pp. 935-940 ◽  
Author(s):  
Gerald Oliver Aspinall ◽  
Hany Kamal Fanous ◽  
Nimal Savitri Kumar ◽  
Velupillai Puvanesarajah
Keyword(s):  
Sodium Borohydride ◽  
Gum Arabic ◽  
Lead Tetraacetate ◽  
Oxidative Decarboxylation ◽  
Hydroxyl Groups ◽  
Reaction Sequence ◽  
Pectic Acid ◽  
Acid Methyl ◽  
Sterculia Urens ◽  
Derivatives Of

Reaction of permethylated glycopyranosiduronic acids with lead tetraacetate furnishes epimeric 5-acetoxypentopyranosides as products of oxidative decarboxylation. Glycoside cleavage then occurs on treatment with sodium borohydride which affords the corresponding pentitols with exposure of aglyconic hydroxyl groups. The reaction sequence has been performed with permethylated derivatives of methyl β-melibiosiduronic acid, methyl β-gentiobiosiduronic acid, gum arabic, leiocarpan A, Sterculia urens gum, and citrus pectic acid. The scope of the reaction sequence in polysaccharide studies is discussed.

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