Ptp2

Ptp2 is a cytosolic, non-receptor protein tyrosine phosphatase encoded by the PTP2 gene in Saccharomyces cerevisiae. It belongs to the classical protein tyrosine phosphatase family and contains the characteristic catalytic motif HCX5R in its active site, with a catalytic cysteine essential for dephosphorylation. Ptp2 participates in the regulation of the high-osmolarity glycerol (HOG) MAP kinase pathway by removing phosphates from tyrosine residues on target proteins, thereby contributing to the termination of signaling after osmotic stress.

In the HOG pathway, Ptp2 acts to attenuate Hog1 activation, helping to balance the cellular response to changes in osmolarity. It works in conjunction with related phosphatases such as Ptp3 to fine-tune Hog1 signaling, ensuring appropriate adaptation without prolonged or inappropriate pathway activity. The enzyme is primarily found in the cytosol, and its activity can be influenced by growth conditions and stress.

Genetic and biochemical studies in yeast show that loss or reduction of Ptp2 function alters the dynamics of Hog1 phosphorylation and can affect osmotolerance and glycerol production, underscoring its role in signal termination rather than initiation. Orthologous PTP enzymes with similar function and catalytic motifs are observed in other fungi, though exact roles can vary by species and context.

Beyond yeast, Ptp2-like phosphatases are of interest for understanding fungal stress responses and can influence virulence and environmental resilience in pathogenic fungi. They are also studied to illuminate general principles of MAP kinase regulation by phosphatases.

See also: protein tyrosine phosphatase; Hog1; Ptp3.