# An unexpected role of EasDaf: catalyzing the conversion of chanoclavine aldehyde to chanoclavine acid

## TL;DR

This study reveals that the enzyme EasDaf plays a dual role in converting a compound into two different forms, which helps understand the complex production of ergot alkaloids.

## Contribution

The paper discovers that EasDaf catalyzes two sequential oxidations to convert CC to CC acid, revealing a new enzymatic function.

## Key findings

- EasDaf converts CC aldehyde to CC acid through two sequential oxidations.
- Amino acids Y166 and S153 are crucial for EasDaf's catalytic mechanism.
- Molecular docking and site-directed mutagenesis confirmed the roles of Y166 and S153.

## Abstract

Ergot alkaloids (EAs) are a diverse group of indole alkaloids known for their complex structures, significant pharmacological effects, and toxicity to plants. The biosynthesis of these compounds begins with chanoclavine-I aldehyde (CC aldehyde, 2), an important intermediate produced by the enzyme EasDaf or its counterpart FgaDH from chanoclavine-I (CC, 1). However, how CC aldehyde 2 is converted to chanoclavine-I acid (CC acid, 3), first isolated from Ipomoea violacea several decades ago, is still unclear. In this study, we provide in vitro biochemical evidence showing that EasDaf not only converts CC 1 to CC aldehyde 2 but also directly transforms CC 1 into CC acid 3 through two sequential oxidations. Molecular docking and site-directed mutagenesis experiments confirmed the crucial role of two amino acids, Y166 and S153, within the active site, which suggests that Y166 acts as a general base for hydride transfer, while S153 facilitates proton transfer, thereby increasing the acidity of the reaction.

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EAs possess complicated skeletons and are widely used in several clinical diseases

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EasDaf
belongs to the short-chain dehydrogenases/reductases (SDRs) and converted CC or CC aldehyde to CC acid

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The catalytic mechanism of EasDaf
for dehydrogenation was analyzed by molecular docking and site mutations

The online version contains supplementary material available at 10.1007/s00253-024-13157-8.