Patulin Detoxification by Evolutionarily Divergent Reductases of Gluconobacter oxydans ATCC 621

TL;DR

This study explores how Gluconobacter oxydans detoxifies the mycotoxin patulin using two enzymes, GOX0716 and GOX1462, revealing their properties and evolutionary relationships.

Contribution

The study completes the characterization of all four patulin-detoxifying reductases in Gluconobacter oxydans and reveals their evolutionary divergence and functional differences.

Findings

GOX0716 and GOX1462 detoxify patulin with optimal pHs of 6 and 7, respectively, and are active between 25–55 °C.

GOX0716 is more thermostable than GOX1462, with a half-life of 4.95 hours at 55 °C.

Phylogenetic and molecular analysis shows GOX0716 and GOX1462 belong to distinct enzyme families with unique active site architectures.

Abstract

The mycotoxin patulin
in processed apple juice poses a significant
threat to food safety, driving the need for effective detoxification
strategies. Gluconobacter oxydans ATCC
621 can detoxify patulin to ascladiol using either the short-chain
dehydrogenases/reductases (SDRs)—GOX0525, GOX1899, and GOX0716—or
the aldo-keto reductase (AKR) GOX1462. While GOX0525 and GOX1899 have
been previously characterized, this study focuses on GOX0716 and GOX1462,
evaluating their optimal pH, thermostability, thermoactivity, and
substrate specificity, thereby completing the characterization of
all four reductases. GOX0716 and GOX1462 exhibit pH optima of 6 and
7, respectively, and are functional across a broad temperature range
of 25–55 °C. GOX0716 was determined to be more thermostable
than GOX1462, with a half-life of 4.95 h at 55 °C. Phylogenetic
analysis revealed that these SDRs belong to distinct evolutionary
families with broad substrate specificity. GOX0716 is a member of
the SDR79 family, which shares a common ancestry with the SDR111 family
of fungal anthrol reductases. Conversely, GOX1462 is a member of the
AKR18 family, which is involved in detoxification of the mycotoxin,
deoxynivalenol (DON). Molecular docking analysis of Alphafold models
highlights distinct variations in the active site architectures of
these SDRs and AKRs, offering insights into their differing catalytic
efficiencies toward patulin.

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