Predicting Enzyme pH Optima from Structure Using Equivariant Graph Neural Networks

Enzyme activity and stability are strongly modulated by pH, making the catalytic pH optimum (pH opt) a key parameter in enzyme development and biotechnological applications. Experimental determination of pH opt is, however, labor-intensive and time-consuming, motivating the development of accurate computational prediction methods. Here, we introduce pHoptNN, an E(n)-equivariant graph neural network designed to predict enzyme pH opt directly from three-dimensional protein structures. pHoptNN was trained on a curated dataset comprising nearly 12,000 enzymes with experimentally determined pH opt values and high-confidence structural models obtained from the Protein Data Bank and AlphaFold3. The