ALD5, PAD1, ATF1 and ATF2 facilitate the catabolism of coniferyl aldehyde, ferulic acid and p-coumaric acid in Saccharomyces cerevisiae

Lisbeth Olsson,Maurizio Bettiga,Peter Temitope Adeboye

doi:10.1038/srep42635

Abstract

The ability of Saccharomyces cerevisiae to catabolize phenolic compounds remains to be fully elucidated. Conversion of coniferyl aldehyde, ferulic acid and p-coumaric acid by S. cerevisiae under aerobic conditions was previously reported. A conversion pathway was also proposed. In the present study, possible enzymes involved in the reported conversion were investigated. Aldehyde dehydrogenase Ald5, phenylacrylic acid decarboxylase Pad1, and alcohol acetyltransferases Atf1 and Atf2, were hypothesised to be involved. Corresponding genes for the four enzymes were overexpressed in a S. cerevisiae strain named APT_1. The ability of APT_1 to tolerate and convert the three phenolic compounds was tested. APT_1 was also compared to strains B_CALD heterologously expressing coniferyl aldehyde dehydrogenase from Pseudomonas, and an ald5Δ strain, all previously reported. APT_1 exhibited the fastest conversion of coniferyl aldehyde, ferulic acid and p-coumaric acid. Using the intermediates and conversion products of each compound, the catabolic route of coniferyl aldehyde, ferulic acid and p-coumaric acid in S. cerevisiae was studied in greater detail.

Highlights

Having seen that Pseudomonas and Corynebacterium possess potent oxidoreductases that efficiently convert eugenol via coniferyl aldehyde[11,12,13], we speculated that similar enzymes could be present in S. cerevisiae
We hypothesized that overexpression of ATF1 and ATF2 would improve the conversion of phenolic alcohols formed as intermediates and facilitate the entire catabolic process of coniferyl aldehyde (CA), ferulic acid (FA) and p-coumaric acid (PCA)
We have demonstrated that ALD5 is actively involved in the conversion of coniferyl aldehyde in S. cerevisiae in APT_1

Summary

Introduction

Having seen that Pseudomonas and Corynebacterium possess potent oxidoreductases that efficiently convert eugenol via coniferyl aldehyde[11,12,13], we speculated that similar enzymes could be present in S. cerevisiae. The alcohol acetyl transferases ATF1 and ATF2 are known to be involved in the metabolism of various aromatic esters such as phenyl ethyl acetate and aliphatic esters in S. cerevisiae. ALD5, PAD1, ATF1 and ATF2 were overexpressed on the hypothesis that their corresponding enzymes are active in our previously proposed conversion pathway[5]. This resulted in a new strain of S. cerevisiae named APT_1. To better understand the metabolic consequences of the genetic changes, the strains was thoroughly physiologically characterized This included mapping the phenolic metabolites and studying the effects of CA, FA and PCA on the physiology of the new S. cerevisiae APT_1 strain. APT_1 was compared to strains SC_ald5Δ, B_CALD which we have engineered to heterologously express coniferyl aldehyde dehydrogenase (CALDH) from Pseudomonas sp. strain HR199 and the control strain, all of which we have previously reported[14]

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Conclusion