A screening pipeline to characterize stress-induced enzymes uncovers a cellular function for the poorly characterized alcohol dehydrogenase Bdh2.

Cells possess intricate metabolic networks comprising hundreds of enzymes. Despite extensive research, many of these enzymes remain uncharacterized. Identifying the function of these enzymes is crucial for advancing our understanding of cellular metabolism. However, multiple enzymes are not active in standard conditions, making them challenging to study. To overcome this challenge, we created a pipeline to track the upregulation of enzymes at the protein level during diverse growth conditions, suggesting a requirement for their activity in these conditions. To do this, we assembled a collection of ∼180 yeast strains, each containing an uncharacterized putative enzyme fused to a fluorophore and under the regulation of its own promoter. By subjecting the collection to 42 diverse environments, we identified the biologically relevant conditions for the upregulation of 16 proteins. We focused on one such putative alcohol dehydrogenase, Bdh2, whose expression was upregulated during nutrient-limited conditions, and functionally characterized it. More broadly, our discovery pipeline lays the foundation for uncovering new stress-induced enzymes. This has implications for the cell biology of metabolism and biotechnology.