The oyster mushroom (Pleurotus ostreatus), apart from reducing cholesterol and having anticancerogenic properties, is characterised for its capacity for breaking down cellulose. Finding out which genes are responsible for this activity the reason why the fungus is sometimes used as a decontaminating agent, was the aim of the PhD thesis by Arantza Eizmendi Goikoetxea, which she defended at the Public University of Navarre with the title, Molecular Characterisation of a family of genes of cellobiohydrolases in the "Pleurotus ostreatus" fungus.

Degradation of cellulose

In nature, the oyster mushroom grows on dead trunks of trees where the lignin and cellulose the two principal components of wood - are being broken down. Degradation of lignin has been studied over the years by a number of research teams that have characterised the genes involved. But nobody, to date, has tackled the degradation of cellulose from a molecular perspective.

Cellulose is the most abundant biological polymer on the planet. It is made up of units of D-glucose united by means of glycosidic links that form long polymer chains. The breaking down by live organisms takes place through the action of three types of enzymes: endogluconases, cellobiohydrolases y b-glucosidases.

All these, necessary for the complete breaking down of cellulose, function by hydrolysing the glycoside links, but they vary in the specificity of substrate: the endoglucanases attack the glycosidic links within the cellulose molecule, the cellobiohydrolases act by liberating units of cellobiose from either end of the cellulose chain and the b-glucosidases hydrolyse the cellobiose molecules, producing glucose as end product.

In her PhD thesis Arantza Eizmendi Goikoetxea has analysed the activity of one of these types of enzymes: the cellobiohydrolases. To this end, she cloned, isolated and sequenced those genes of the oyster mushroom responsible for this activity and
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Contact: Irati Kortabitarte
iratik@elhuyar.com
34-943-363-040
Elhuyar Fundazioa
15-Mar-2005

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