Dataset Information

A defence-related Olea europaea ?-glucosidase hydrolyses and activates oleuropein into a potent protein cross-linking agent.

ABSTRACT: Oleuropein, the major secoiridoid compound in olive, is involved in a sophisticated two-component defence system comprising a ?-glucosidase enzyme that activates oleuropein into a toxic glutaraldehyde-like structure. Although oleuropein deglycosylation studies have been monitored extensively, an oleuropein ?-glucosidase gene has not been characterized as yet. Here, we report the isolation of OeGLU cDNA from olive encoding a ?-glucosidase belonging to the defence-related group of terpenoid-specific glucosidases. In planta recombinant protein expression assays showed that OeGLU deglycosylated and activated oleuropein into a strong protein cross-linker. Homology and docking modelling predicted that OeGLU has a characteristic (?/?)8 TIM barrel conformation and a typical construction of a pocket-shaped substrate recognition domain composed of conserved amino acids supporting the ?-glucosidase activity and non-conserved residues associated with aglycon specificity. Transcriptional analysis in various olive organs revealed that the gene was developmentally regulated, with its transcript levels coinciding well with the spatiotemporal patterns of oleuropein degradation and aglycon accumulation in drupes. OeGLU upregulation in young organs reflects its prominent role in oleuropein-mediated defence system. High gene expression during drupe maturation implies an additional role in olive secondary metabolism, through the degradation of oleuropein and reutilization of hydrolysis products.

SUBMITTER: Koudounas K

PROVIDER: S-EPMC4669557 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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A defence-related Olea europaea β-glucosidase hydrolyses and activates oleuropein into a potent protein cross-linking agent.

Koudounas Konstantinos K Banilas Georgios G Michaelidis Christos C Demoliou Catherine C Rigas Stamatis S Hatzopoulos Polydefkis P

Journal of experimental botany 20150219 7

Oleuropein, the major secoiridoid compound in olive, is involved in a sophisticated two-component defence system comprising a β-glucosidase enzyme that activates oleuropein into a toxic glutaraldehyde-like structure. Although oleuropein deglycosylation studies have been monitored extensively, an oleuropein β-glucosidase gene has not been characterized as yet. Here, we report the isolation of OeGLU cDNA from olive encoding a β-glucosidase belonging to the defence-related group of terpenoid-specif ...[more]

PMID: 25697790

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Project description:Olive fruits and oils contain an array of compounds that contribute to their sensory and nutritional properties. Phenolic compounds in virgin oil and olive-derived products have been proven to be highly beneficial for human health, eliciting increasing attention from the food industry and consumers. Although phenolic compounds in olive fruit and oil have been extensively investigated, allowing the identification of the main classes of metabolites and their accumulation patterns, knowledge of the molecular and biochemical mechanisms regulating phenolic metabolism remains scarce. We focused on the role of polyphenoloxidase (PPO), peroxidase (PRX) and β-glucosidase (β-GLU) gene families and their enzyme activities in the accumulation of phenolic compounds during olive fruit development (35-146 days after full bloom), under either full irrigation (FI) or rain-fed (RF) conditions. The irrigation regime affected yield, maturation index, mesocarp oil content, fruit size, and pulp-to-pit ratio. Accumulation of fruit phenolics was higher in RF drupes than in FI ones. Members of each gene family were developmentally regulated, affected by water regime, and their transcript levels were correlated with the respective enzyme activities. During the early phase of drupe growth (35-43 days after full bloom), phenolic composition appeared to be linked to β-GLU and PRX activities, probably through their effects on oleuropein catabolism. Interestingly, a higher β-GLU activity was measured in immature RF drupes, as well as a higher content of the oleuropein derivate 3,4-DHPEA-EDA and verbascoside. Activity of PPO enzymes was slightly affected by the water status of trees during ripening (from 120 days after full bloom), but was not correlated with phenolics content. Overall, the main changes in phenolics content appeared soon after the supply of irrigation water and remained thereafter almost unchanged until maturity, despite fruit growth and the progressive decrease in pre-dawn leaf water potential. We suggest that enzymes involved in phenolic catabolism in the olive fruit have a differential sensitivity to soil water availability depending on fruit developmental stage.

Dataset Information

A defence-related Olea europaea ?-glucosidase hydrolyses and activates oleuropein into a potent protein cross-linking agent.

Publications

A defence-related Olea europaea β-glucosidase hydrolyses and activates oleuropein into a potent protein cross-linking agent.

Similar Datasets

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