Caffeic Acid Cycle (CAC) in fungal bioluminescence: luciferin antioxidant effect, oxyluciferin recycling and oxidative stress

Abstract

Recently with the discovery of the structure of fungal luciferin it became possible to know a secondary pathway for the expression of bioluminescence called Caffeic Acid Cycle (CAC). Caffeic acid, generated in fungi from tyrosine in the Shikiimate pathway is the initial substrate for the formation of hispidin by the enzyme complex hispidin synthase (HispS). Hydroxylation of hispidin by a soluble hydroxylase, hispidine-3-hydroxylase (H3H), yields fungal luciferin which, upon the addition of an oxygen molecule by luciferase (Luz), forms the high energy intermediate, an endoperoxide. The intermediate is decomposed into light and the product, oxyluciferin (caffeylpyruvate), is recycled to caffeic acid through caffeylpyruvate hydrolase (CPH). These intermediates are known to be antioxidants, which could suggest their involvement as a complementary defense to the classic cellular oxidative stress protection system. Yeasts were transformed by molecular biology techniques to express CAC enzymes, expanding the methodologies to try to understand the biological role of bioluminescence, besides attracting spore-dispersing animals in the case of mushrooms. In addition, the introduction of CAC genes into a non-bioluminescent basidiomycete would provide tools for understanding the role of bioluminescence in fungi in their reproductive life stage. This project aims to clone and characterize CAC enzymes, to check for genetically modified yeast alterations to this system under oxidative stress conditions, to study luciferin as a possible antioxidant and the transformation of a non-bioluminescent basidiomycete into bioluminescent using CAC system. (AU)