Enzymes are biological macromolecules that catalyze chemical reactions in living organisms. They are primarily composed of proteins but can also be composed of ribonucleic acids (RNA) in the case of ribozymes. Each enzyme has a specific active site that binds to its substrate, facilitating the transformation of substrates into products. The specificity of an enzyme is influenced by its structure, including the interactions of its side chains and any cofactors that may assist in enzyme activity. In this context, consider the enzymatic mechanisms and the structural modifications of biomolecules that can lead to variations in activity.

A common example is the enzyme lactate dehydrogenase (LDH), which catalyzes the conversion of pyruvate to lactate. Variations in the structure of LDH can lead to differences in substrate binding affinities and catalytic efficiencies. Consider how biochemical modifications to the enzyme might affect its function.

Which of the following modifications would most likely enhance the catalytic activity of an enzyme like lactate dehydrogenase?