Cell Wall Peroxidase Activity Research Articles

Peroxidase Activity in the Leaf Elongation Zone of Tall Fescue

Previous work suggested that cell wall peroxidase activity increased as cells were displaced through the elongation zone in leaf blades of tall fescue (Festuca arundinacea Schreb.). In this study, two genotypes that differ in length of the elongation zone were used to examine the relationship between peroxidase activity in apoplastic fluid of intact leaf blade segments and the spatial distribution of leaf growth. Apoplastic fluid was extracted by vacuum infiltration and centrifugation, and peroxidase activity was assayed spectrophotometrically. Isoelectric focusing was used to characterize the isoforms of apoplastic peroxidase within the region of elongation and in the region of secondary cell wall deposition, which is distal to the elongation zone. A striking correlation was found in each genotype between both the location and timing of increase in apoplastic peroxidase activity and the onset of growth deceleration. Only cationic isoforms of apoplastic peroxidase could be identified in the elongation zone, whereas additional anionic isoforms appeared in the region of secondary cell wall deposition. We conclude that cessation of elongation growth in tall fescue leaf blades is likely to be related to the secretion of cationic isoforms of peroxidase into the cell wall.

Superoxide anion and hydrogen peroxide metabolism in soybean embryonic axes during germination

The total rate of mitochondrial O 2 − production in the presence of NADH as substrate increased from 200 to 1340 pmol/min per axis between 2 and 30 h of imbibition. The activities of the enzymes involved in hyperoxide metabolism, e.g., superoxide dismutase, catalase, peroxidase and glutathione and ascorbate peroxidases, markedly changed during the germination of soybean embryonic axes. Superoxide dismutase was the enzymatic activity affected the most during the initial stages of germination. Intracellular O 2 − steady-state concentration, calculated from the rate of O 2 − production and superoxide dismutase activity, showed a 2-fold increase from 2 · 10 −8 M to 4 · 10 −8 M in germination phase I, declined in phase II to 2 · 10 −8 M and remained constant over the rest of the incubation period. The reaction of H 2O 2 and luminol catalyzed by Co 2+ was utilized to measure H 2O 2 diffused out of the soybean axes after 5 to 10 min of incubation. The catalase-sensitive luminol emission of diffusates prepared from axes previously imbibed from 2 to 30 h corresponded to a H 2O 2 intracellular steady-state concentration in the range of 0.3 to 0.9 μM. The activity of metal-containing antioxidant enzymes was determined in the extracellular fluid. Cell wall peroxidase activity increased from 10 to 300 μmol/min per mg protein and appears as a potentially important pathway for H 2O 2 utilization. Hydrogen peroxide metabolism in soybean embryonic axes during early imbibition appears to have the following main features: (a) mitochondrial membranes are the most important source of cytosolic O 2 − and H 2O 2; (b) H 2O 2 is regulated at a steady-state concentration of 0.3–0.9 μM; (c) catalase is the main enzyme in terms of H 2O 2 utilization; (d) H 2O 2 exo-diffusion is quantitatively important destiny of intracellular H 2O 2; and (e) extracellular peroxidase located at the cell wall affords an enzymatic system able to use diffused H 2O 2.

Oxidation of coniferyl alcohol by cell wall peroxidases at the expense of indole-3-acetic acid and O 2: A model for the lignification of plant cell walls in the absence of H 2O 2

The oxidation of coniferyl alcohol (CA), a lignin precursor, by cell wall peroxidases may take place at the expense of indole-3-acetic acid (IAA) and O 2, and in the absence of H 2O 2. The peroxidase-catalyzed oxidation of CA shows an optimum at an IAA concentration of 0.33 mM, while higher IAA concentrations are inhibitory. The observation that the oxidation of CA by cell wall peroxidase at the expense of IAA and O 2 is inhibited by genistein, a putative endogenous inhibitor of lignification in lupin hypocotyls, supports the view that the H 2O 2-generating system coexists with cell wall peroxidase activities involved in lignification, and that it takes place at the expense of IAA and O 2.

Distribution of isoflavones in lupin hypocotyls. Possible control of cell wall peroxidase activity involved in lignification

Distribution of isoflavones in lupin hypocotyls. Possible control of cell wall peroxidase activity involved in lignification

Distribution of isoflavones in lupin hypocotyls. Possible control of cell wall peroxidase activity involved in lignification

The distribution of 4 key isoflavones (luteone, genistein, 2'-hydroxygenistein and wighteone) in lupin (Lupinus albus L. cv. multolupa) hypocotyls shows a gradient that diminishes from young to old tissues. A spatial gradient occurs within the hypocotyl, and a temporal gradient in both the outermost vascular and epidermal tissues. Not only does a gradient exist in respect to the quantity of isoflavones, but there is also a gradient in respect to the type of isoflavone. Thus, wighteone is mainly associated with the non-meristematic zones of the lupin hypocotyl. A close relationship was found between the distribution and the localization in the walls of phloem cells of both peroxidase (EC 1.11.1.7) and isoflavones. This observation suggests an in vivo peroxidase-isoflavone interconnection. In fact, lupin isoflavones are able to inhibit the peroxidase-catalyzed oxidation of the lignin precursor coniferyl alcohol, probably due to the co-oxidation of isoflavones in the reaction media. The results are discussed on the basis of a possible role for isoflavones in controlling cell wallperoxidase activity involved in the lignification of phloem cells.

Control by pH of Cell Wall Peroxidase Activity Involved in Lignification

pH affected both conyferyl alcohol (CA) oxidation and NADH-dependent H2O2 formation catalysed by cell wall-bound peroxidase from lupin. The kinetics of CA oxidation shown at pH 5.0 was of the Michaelian-type, independently of the physical state (bound or soluble) of the enzyme in the cell wall, whereas at pH 8.0, it was cooperative. The affinity of the enzyme to H2O2and the rate of H2O2 formation were higher at pH 8.0 than at pH 5.0. The kinetics of H2O2 formation at pH 8.0 was strongly cooperative. These results are discussed with respect to the important role of pH in the regulation of cell wall peroxidase activities involved in lignification.

Relation of cell wall peroxidase activity with growth in epicotyls of Cicer arietinum. Effects of calmodulin inhibitors

Sánchez, O.J., Pan, A., Nicolás, G. and Labrador, E. 1989. Relation of cell wall peroxidase activity with growth in epicotyls of Cicer arietinum. Effects of calmodulin inhibitors.Peroxidases are bound ionically to cell walls in epicotyls of Cicer arietinum L. cv. Castellana. The cell wall peroxidase activity increases during the growth of epicotyls, being the lowest in 3‐day‐old epicotyls with high growth capacity. The cell wall phenolic compounds, postulated natural substrates of cell wall peroxidases, also increase during growth.The calmodulin inhibitors chlorpromazine and trifluoperazine decrease the elongation rate of epicotyls of Cicer arietinum. These inhibitors also cause an increase in the cell wall peroxidase activity and in the level of phenolic compounds. A possible regulatory effect of calmodulin on peroxidase activity is postulated.

Inhibition of Stem Elongation in Cucumis Seedlings by Blue Light Requires Calcium

The effects of blue light and calcium on elongation of hypocotyl segments of Cucumber (Cucumis sativa L. cv Burpee's Pickler) were studied. Cucumber seedlings grown in dim red light showed a rapid decline in the rate of hypocotyl elongation when irradiated with high intensity (100 micromoles per square meter per second) blue light. In intact, 4-day-old seedlings the inhibition began within 2 minutes after the onset of blue-light irradiation and reached a maximum of approximately 55% within 4 minutes. Hypocotyl segments cut from 4-day-old seedlings also showed an inhibition of elongation in response to blue light when segments were floated on aqueous buffer and exposed to blue light for 3 hours. In the presence of 2 micromolar indole-3-acetic acid, blue light caused a 50% inhibition of elongation. Buffering free calcium in the incubation medium with 0.1 millimolar ethylene glycol bis(-aminoethyl ether)- N,N,N',N'-tetraacetic acid eliminated the blue-light inhibition of segment elongation. Several experiments confirmed a specific requirement for calcium for the blue-light-induced inhibition of segment elongation. Treating segments with 0.2 micromolar fusicoccin abolished the inhibition of elongation by blue light as did buffering the medium at pH 4. Adding 1 millimolar ascorbate to incubation medium also eliminated the inhibition of segment elongation caused by blue light. Several compounds implicated in cell-wall redox reactions alter the magnitude of the blue-light-induced inhibition. The activity of peroxidase isolated from the cell-wall free space of cucumber hypocotyls was inhibited by ascorbate and low pH. The results are consistent with the hypothesis that blue light inhibits elongation by inducing an increase in cell-wall peroxidase activity and implicate calcium ions in the response to blue light.

Isolation and characterization of Populus isoperoxidases involved in the last step of lignin formation

Peroxidases (EC 1.11.1.7) from Populus x euramericana were investigated during the dormant and growing seasons using histochemical and biochemical methods. The activities of syringaldazine oxidase and p-paraphenylenediamine-pyrocatechol oxidase in sections of branches were maximal during spring in both phloem and young xylem. Cytoplasmic and cell-wall peroxidase activities from different lignified tissues were estimated in vitro. Pronounced differences were noticed between fractions isolated during spring and winter. Gel electrophoresis showed the presence of an anionic fast-migrating isoperoxidase group with a high syringaldazine-oxidase activity. The isoenzymes of this group were different in winter and in spring. The properties of these isoperoxidases (kinetic constants, pH optimum, resistance to heat) were investigated after isolation by ion-exchange chromatography.