Role of pectic and cellulolytic enzymes in the invasion of the soybean by Rhizobium japonicum

1975 ◽  
Vol 21 (8) ◽  
pp. 1254-1258 ◽  
Author(s):  
William J. Hunter ◽  
Gerald H. Elkan
Keyword(s):  
Enzyme Activity ◽  
Indoleacetic Acid ◽  
Methyl Cellulose ◽  
Rhizobium Japonicum ◽  
Cellulolytic Enzymes ◽  
Pectic Acid ◽  
Pectic Enzyme ◽  
Seedling Inoculation

Past workers have suggested pectic enzyme involvement in the invasion of legumes by Rhizobium. However, no role for pectic acid, pectin, or methyl cellulose depolymerase enzymes in the invasion of R. japonicum was suggested by the current study. Seedling inoculation with infective bacteria did not result in increased enzyme activity. Rhizobium japonicum cell-free culture extracts and 3-indoleacetic acid did not affect the activation, induction, or binding of these enzymes.

Evidence for the role of carboxyl groups in activity of endopolygalacturonase of Aspergillus niger. Chemical modification by carbodiimide reagent

1990 ◽  
Vol 55 (5) ◽  
pp. 1389-1395 ◽  
Author(s):  
Lubomíra Rexová-Benková
Keyword(s):  
Enzyme Activity ◽  
Aspergillus Niger ◽  
Competitive Inhibitor ◽  
Enzyme Inactivation ◽  
Pectic Acid ◽  
Tyrosine Residues ◽  
Group Modification ◽  
Glycine Ethyl Ester ◽  
Decreasing Ph

Endopolygalacturonase (E.C. 3.2.1.15) of Aspergillus niger was modified with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and glycine ethyl ester. The modification resulted in total irreversible inactivation of the enzyme and derivatization of carboxyl acid residues and tyrosine residues. The treatment of the modified enzyme with hydroxylamine led to a restoration of modified tyrosine residues but not to reactivation of the enzyme. The inactivation with carbodiimide was pH dependent, the rate of inactivation increased with decreasing pH. Tri(D-galactosiduronic acid), a competitive inhibitor, or crosslinked pectic acid protected the enzyme against the inactivation. In bioaffinity chromatography of partially inactivated endopolygalacturonase, all residual enzyme activity was retained on the adsorbent while all inactive fraction passed without retardation through the column. On the basis of these results, as well as proximity of the rate constants for enzyme inactivation and the carboxyl group modification it is suggested that the loss of endopolygalacturonase activity is due to the modification of carboxylic acid residues and that at least one is essential for enzyme activity.

Evidence countering the role of polygalacturonase in invasion of root hairs of leguminous plants by Rhizobium spp.

1968 ◽  
Vol 14 (6) ◽  
pp. 617-625 ◽  
Author(s):  
Thomas T. Lillich ◽  
Gerald H. Elkan
Keyword(s):  
Enzyme Activity ◽  
Glycine Max ◽  
Sole Carbon Source ◽  
Root Hairs ◽  
Rhizobium Japonicum ◽  
Leguminous Plants ◽  
Uninoculated Control ◽  
Rhizobium Spp ◽  
Polygalacturonase Activity

Polygalacturonase has been postulated as being involved in the invasion of the host legume by Rhizobium spp. The role of this enzyme in the invasion of Glycine max by Rhizobium japonicum was investigated. Enzyme activity of several Rhizobium spp. was assayed viscometrically and no constitutive polygalacturonase was found. The enzyme could not be induced by growth with either pectin or galactose as the sole carbon source. Extract and exudate from the roots of nodulating and nonnodulating strains of Glycine max that had been incubated with effective strains of R. japonicum failed to show any higher levels of polygalacturonase activity than did uninoculated control plants. Previously reported experiments were duplicated. Levels of polygalacturonase activity from the extract and exudate of white clover inoculated with R. trifolii Cl 226 were as reported in the literature. Contrary to published reports, however, no greater levels of enzyme activity were found from effective plant–bacteria associations than from either ineffective associations or uninoculated control plants. It was concluded from these experiments that polygalacturonase does not play a major role in the invasion of Glycine max by Rhizobium japonicum.

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.

A possible role of arginase in the regulation of polyamine biosynthesis in the rat thyroid

1981 ◽  
Vol 98 (1) ◽  
pp. 57-61 ◽  
Author(s):  
Shigeru Matsuzaki ◽  
Mitsuo Suzuki ◽  
Koei Hamana
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Arginase Activity ◽  
Polyamine Biosynthesis ◽  
Rat Thyroid ◽  
Arginine Concentration

Abstract. Effect of chronic methylthiouracil (MTU) treatment on the thyroid arginase activity and thyroidal concentration of arginine, ornithine and other amino acids was studied in the rat. The activity of thyroid arginase increased significantly at 15 days of MTU treatment and the elevated enzyme activity was reduced to normal by l-thyroxine (T4) injection. The thyroidal concentration of polyamines was increased by MTU and decreased by T4 with the exception of spermine. The thyroidal concentration of arginine and lysine, a substrate and an inhibitor for arginase respectively decreased significantly, while that of ornithine remained unchanged after MTU treatment. T4 injected to MTU-pretreated rats restored the decreased arginine concentration to normal. These results suggest that ornithine supply for polyamine biosynthesis is regulated by the level of both arginase and lysine in the thyroid.

Inhibition of cambial activity in Abies balsamea by internal water stress: role of abscisic acid

1975 ◽  
Vol 53 (24) ◽  
pp. 3041-3050 ◽  
Author(s):  
C. H. A. Little
Keyword(s):  
Abscisic Acid ◽  
Water Stress ◽  
Indoleacetic Acid ◽  
Stomatal Closure ◽  
Abies Balsamea ◽  
Cambial Activity ◽  
Inhibitory Effect ◽  
Internal Water ◽  
Endogenous Aba

In experiments with attached and detached shoots of balsam fir, Abies balsamea L., synthetic (±)abscisic acid (ABA) (1) reduced photosynthesis and transpiration by inducing stomatal closure, (2) inhibited indoleacetic acid (IAA) - induced cambial activity in photosynthesizing and non-photosynthesizing shoots, and (3) inhibited the basipetal movement of [14C]IAA. Neither gibberellic acid nor kinetin counteracted the inhibitory effect of (±)ABA on IAA-induced cambial activity. In addition it was demonstrated that increasing the internal water stress increased the level of endogenous ABA in the phloem–cambial region of bark peelings and decreased the basipetal movement of [14C]IAA through branch sections. On the basis of these findings it is proposed that internal water stress inhibits cambial activity, partly through increasing the level of ABA; the ABA acts to decrease the provision of carbohydrates and auxin that are required for cambial growth.

Protective role of Bacopa monniera on morphine-induced brain mitochondrial enzyme activity in rats

Fitoterapia ◽  
2002 ◽  
Vol 73 (5) ◽  
pp. 381-385 ◽  
Author(s):  
T. Sumathy ◽  
S. Govindasamy ◽  
K. Balakrishna ◽  
G. Veluchamy
Keyword(s):  
Enzyme Activity ◽  
Protective Role ◽  
Mitochondrial Enzyme ◽  
Bacopa Monniera
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