Biomedical subjects

M López-Serrano

Publications and source records attributed to M López-Serrano.

9 recordsLinked to original sources

PubMed2004

Zinnia elegans uses the same peroxidase isoenzyme complement for cell wall lignification in both single-cell tracheary elements and xylem vessels.

The nature of the peroxidase isoenzyme complement responsible for cell wall lignification in both Zinnia elegans seedlings and Z. elegans tracheary single-cell cultures have been studied. Results showed that both hypocotyls and stems from lignifying Z. elegans seedlings express a cell wall-located basic peroxidase of pI approximately 10.2, which was purified to homogeneity. Molecular mass determination under non-denaturing conditions showed an M(r) of about 43 000, similar to that of other plant peroxidases. The purified Z. elegans peroxidase showed absorption maxima at 403 (Soret band), and at 496-501 and 632-635 (alpha and beta absorption bands), indicating that this enzyme is a high spin ferric haem protein, belonging to the plant peroxidase superfamily, the prosthetic group being ferric protoporphyrin IX. The N-terminal amino acid sequence of this Z. elegans basic peroxidase was KVAVSPLS (peptide motif in bold), which shows strong homologies with the N-amino acid terminus of other strongly basic plant peroxidases. Isoenzyme and western blot analyses showed that this peroxidase isoenzyme is also expressed in trans-differentiating Z. elegans tracheary single-cell cultures. The results also showed that Z. elegans tracheary single-cell cultures not only express the same peroxidase isoenzyme as the Z. elegans lignifying xylem, but that this peroxidase isoenzyme acts as a marker of tracheary element differentiation in Z. elegans mesophyll single-cell cultures. From these results, it may be concluded that Z. elegans uses a single programme, i.e. an identical peroxidase isoenzyme complement, for lignification of the xylem, regardless of the existence of different ontogenesis pathways from either mesophyll cells (in the case of tracheary elements) or cambial derivatives (in the case of xylem vessels).

Asteraceae↗

PubMed2002

Comparative study of the products of the peroxidase-catalyzed and the polyphenoloxidase-catalyzed (+)-catechin oxidation. Their possible implications in strawberry (Fragaria x ananassa) browning reactions.

The peroxidase- and polyphenoloxidase-catalyzed oxidations of (+)-catechin yield several products showing different degrees of polymerization, which are apparently responsible for the pigment decay and the associated browning reaction that occurs in processed strawberry fruits and their derived foods. In this work, we have purified both peroxidase and polyphenoloxidase from Oso Grande cv. strawberry fruits, and comparatively analyzed the products of their enzyme-mediated (+)-catechin oxidation. The joint analysis by reversed-phase and size-exclusion HPLC of the (+)-catechin oxidation products obtained with both enzymes indicate that they were qualitatively the same: dehydrodicatechin B4, a (+)-catechin quinone methide, dehydrodicatechin A, a (+)-catechin trimer, and a (+)-catechin oligomer with polymerization degree equal to or greater than 5. The main quantitative differences between the oxidative reactions were the great amount of oligomer formed in the case of the polyphenoloxidase-mediated reaction and the low amount of (+)-catechin reacted in the case of the peroxidase-mediated reaction. One of the possible reasons for such low levels of (+)-catechin consumption in the case of the peroxidase-mediated reaction was the possible inhibition by products of the enzyme-catalyzed oxidation. In fact, the peroxidase-mediated (+)-catechin oxidation was differentially inhibited by dehydrodicatechin A, showing a competitive type inhibition and a k(I) of 6.4 microM. In light of these observations, these results suggest that brown polymer formation, estimated as oligomeric compounds resulting from (+)-catechin oxidation, in strawberries is mainly due to polyphenoloxidase, and although peroxidase also plays an important role, it is apparently auto-regulated by product (dehydrodicatechin A) inhibition.

Catechin↗

PubMed2001

Reversed-phase and size-exclusion chromatography as useful tools in the resolution of peroxidase-mediated (+)-catechin oxidation products.

The peroxidase-catalysed oxidation of plant phenolics involves one-electron oxidation reactions, and yields unstable mono-radical species, which couple to generate heterogeneous product mixtures of different degrees of polymerisation. One such phenolic susceptible to oxidation by peroxidase is (+)-catechin. Low-pressure chromatography on Sephadex LH-20, using methanol as mobile phase, resolves the main peroxidase-mediated (+)-catechin oxidation products into a dimeric compound (dehydrodicatechin A) and an oligomeric fraction with a polymerisation degree equal or greater than 5. These pure fractions were used to develop rapid high-performance liquid chromatographic methods, both reversed-phase and size-exclusion chromatography for the direct analysis of the peroxidase-mediated (+)-catechin oxidation products. The joint use of both chromatographic systems permitted the qualitative and quantitative identification of the peroxidase-mediated (+)-catechin oxidation products, and can thus be considered as a useful tool for analysing the complex mixtures of natural bioactive plant products synthesized in reactions catalyzed by plant peroxidases.

Catechin↗

PubMed2001

Primary transcripts of ndhD of Liliaceae and Aloaceae require editing of the start and 20th codons.

About 350 nucleotide sequences around the start codon of the plastid ndhD gene were determined in six species to investigate the requirement of C to U editing of the cryptic start codons. The comparison with other sequences in databanks showed that, in contrast to grasses and similarly to dicots, Liliaceae and Aloaceae require editing of the primary transcript to generate the AUG start codon. Primary transcripts of Liliaceae and Aloaceae also show a new editing site at the 59th nucleotide, which has not been described in other plants. In some cases, transcripts showed partial editing which suggests that the synthesis of the protein may be controlled at the level of transcript processing.

Amino Acid Sequence↗

PubMed1999

H(2)O(2)-mediated pigment decay in strawberry as a model system for studying color alterations in processed plant foods.

Phenolic and pigment (anthocyanin) stability in processing-ripe strawberries in response to aging under mildly oxidizing conditions, provoked by exogenous application of H(2)O(2), has been studied to design a simplified model system to study color alterations (pigment decay) that occur in strawberry-derived foods during processing and storage. The results showed that phenolic metabolism in strawberry slices during aging under mildly oxidizing conditions may be either oxidative (independent of exogenous H(2)O(2)) or peroxidative (dependent on exogenous H(2)O(2)), and that feeding strawberry slices with H(2)O(2) stimulates the oxidative phenomena which take place in their absence, such as the processes of anthocyanin and catechin degradation. The results also showed that because both (+)-catechin and anthocyanin levels in strawberry slices fall as H(2)O(2) increases, both p-hydroxybenzoic acid and brown polymeric compounds are formed. Comparison of these results with controls in the absence of H(2)O(2) suggests that peroxidase may play an important role in catechin consumption and in anthocyanin degradation and brown polymer formation during the aging of strawberry slices under mildly oxidizing conditions.

Color↗

PubMed1998

Purification and characterization of alpha-3',4'-anhydrovinblastine synthase (peroxidase-like) from Catharanthus roseus (L.) G. Don.

An H2O2-dependent enzyme capable of coupling catharanthine and vindoline into alpha-3',4'-anhydrovinblastine (AVLB) was purified to apparent homogeneity from Catharanthus roseus leaves. The enzyme shows a specific AVLB synthase activity of 1.8 nkat/mg, and a molecular weight of 45.40 kDa (SDS-PAGE). In addition to AVLB synthase activity, the purified enzyme shows peroxidase activity, and the VIS spectrum of the protein presents maxima at 404, 501 and 633 nm, indicating that it is a high spin ferric heme protein, belonging to the plant peroxidase superfamily. Kinetic studies revealed that both catharanthine and vindoline were substrates of the enzyme, AVLB being the major coupling product.

Chromatography, Affinity↗

PubMed1995

Effect of fosetyl-A1 on peroxidase from grapevine (Vitis vinifera) cells.

Grapevine (Vitis vinifera cv. Monastrell) suspension cell cultures were treated with fosetyl-A1, a widely used systemic fungicide for grapevine diseases caused by oomycetes, and examined at the electron microscope level for peroxidase cytochemistry. The results showed that treatment with fosetyl-A1 provokes an activation of both vacuolar sap and tonoplast-located peroxidase, already described as due to the basic peroxidase isoenzyme, B5, which was previously characterized as a constitutive marker of disease resistance against Plasmopara viticola in axillary bud cultures of Vitis spp. This activation of peroxidase isoenzyme B5, as seen at the electron microscope level, was confirmed by cytophotometric methods, but is in contrast with the unchanged enzyme level determined by biochemical methods. These results suggest a metabolic activation of peroxidase isoenzyme B5 as a consequence of fosetyl-A1 treatment, probably due to an acidification of the vacuole. This response was accompanied by the appearance of myelin-like structures inside the cytoplasm and osmiophylic-bodies inside the mitochondria. However, the latter structural changes cannot easily be related to the above described specific peroxidase response.

Biotransformation↗

PubMed1994

Tentative evidence of a rosmarinic acid peroxidase in cell cultures from lavandin (Lavandula x intermedia) flowers.

The oxidative stability of rosmarinic acid (alpha-O-caffeoyl-3,4-dihydroxyphenyllactic acid) in lavandin (Lavandula x intermedia) cell cultures was studied in an attempt to explain the decrease in the rosmarinic acid content of aging cell cultures, a process which is associated with the appearance of brown pigments. The oxidation of rosmarinic acid by a partially purified protein fraction was followed spectrophotometrically and by HPLC. The results showed that rosmarinic acid oxidation was almost totally dependent on the presence of H2O2 and protein, and that brownish products were the results of this oxidation, resembling those shown by aging cell cultures. Since this protein fraction contains peroxidase activities and shows the total absence of tropolone-sensitive polyphenoloxidase (catecholase) and laccase activities, rosmarinic acid oxidation is tentatively proposed to be caused by a peroxidase-like activity. These results support the existence of a rosmarinic acid peroxidase in cell cultures of lavandin flowers, which may be involved in the oxidative destruction of rosmarinic acid, and which may also be responsible for the formation of brown pigments during aging, lowering the yields of rosmarinic acid.

Cells, Cultured↗

PubMed1992

[Immunizations in hospitalized and outpatient children: the reduction of lost vaccination opportunities].

Among the strategies directed towards the control of preventable illnesses through vaccination, are the "National Days for Vaccination" and the intensive campaigns for country-wide vaccination, which have been taking place in our country during the last few years. An important aspect that must be taken into account is the immunization of children or patients who are hospitalized or those are under medical supervision due to changing chronic pathologies which have is some way interfered with the normal course of the application of the basic scheme of immunizations. The causes which have lead to incomplete vaccination schemes or to unstarted ones have been analyzed in different studies. In many cases, it has been observed that the information available to parents as well as to health workers in inexact. Hospitalization per se does not constitute a contraindication for vaccination, except in certain circumstances where there is some relation to the type of vaccine, as for example that of live attenuated virus or the existence of an underlying disease, like neoplasms and congenital or acquired immunodeficiency, which should be individually studied to evaluate the application of the vaccine depending on each individual case.

Child↗