Discovery and Functional Characterization of a Yeast Sugar Alcohol Phosphatase

Sugar alcohols (polyols)
exist widely in nature. While some specific
sugar alcohol phosphatases are known, there is no known phosphatase
for some important sugar alcohols (e.g., sorbitol-6-phosphate). Using
liquid chromatography–mass spectrometry-based metabolomics,
we screened yeast strains with putative phosphatases of unknown function
deleted. We show that the yeast gene YNL010W, which
has close homologues in all fungi species and some plants, encodes
a sugar alcohol phosphatase. We term this enzyme, which hydrolyzes
sorbitol-6-phosphate, ribitol-5-phosphate, and (d)-glycerol-3-phosphate, polyol phosphatase 1 or PYP1. Polyol phosphates are structural
analogs of the enediol intermediate of phosphoglucose isomerase (Pgi).
We find that sorbitol-6-phosphate and ribitol-5-phosphate inhibit
Pgi and that Pyp1 activity is important for yeast to maintain Pgi
activity in the presence of environmental sugar alcohols. Pyp1 expression
is strongly positively correlated with yeast growth rate, presumably
because faster growth requires greater glycolytic and accordingly
Pgi flux. Thus, yeast express the previously uncharacterized enzyme
Pyp1 to prevent inhibition of glycolysis by sugar alcohol phosphates.
Pyp1 may be useful for engineering sugar alcohol production.