Identification of phenolic compounds in isolated vacuoles of the medicinal plant Catharanthus roseus and their interaction with vacuolar class III peroxidase: an H2O2 affair?
J Exp Bot
; 62(8): 2841-54, 2011 May.
Article
em En
| MEDLINE
| ID: mdl-21357771
ABSTRACT
Class III peroxidases (Prxs) are plant enzymes capable of using H(2)O(2) to oxidize a range of plant secondary metabolites, notably phenolic compounds. These enzymes are localized in the cell wall or in the vacuole, which is a target for secondary metabolite accumulation, but very little is known about the function of vacuolar Prxs. Here, the physiological role of the main leaf vacuolar Prx of the medicinal plant Catharanthus roseus, CrPrx1, was further investigated namely by studying its capacity to oxidize co-localized phenolic substrates at the expense of H(2)O(2). LC-PAD-MS analysis of the phenols from isolated leaf vacuoles detected the presence of three caffeoylquinic acids and four flavonoids in this organelle. These phenols or similar compounds were shown to be good CrPrx1 substrates, and the CrPrx1-mediated oxidation of 5-O-caffeoylquinic acid was shown to form a co-operative regenerating cycle with ascorbic acid. Interestingly, more than 90% of total leaf Prx activity was localized in the vacuoles, associated to discrete spots of the tonoplast. Prx activity inside the vacuoles was estimated to be 1809 nkat ml(-1), which, together with the determined concentrations for the putative vacuolar phenolic substrates, indicate a very high H(2)O(2) scavenging capacity, up to 9 mM s(-1). Accordingly, high light conditions, known to increase H(2)O(2) production, induced both phenols and Prx levels. Therefore, it is proposed that the vacuolar couple Prx/secondary metabolites represent an important sink/buffer of H(2)O(2) in green plant cells.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fenóis
/
Plantas Medicinais
/
Vacúolos
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Peroxidase
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Catharanthus
/
Peróxido de Hidrogênio
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Idioma:
En
Revista:
J Exp Bot
Assunto da revista:
BOTANICA
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Espanha