Peptide and protein substrates

Peptide and protein substrates refers to the broad class of amino acid-based molecules that serve as the functional reactants for enzymes such as kinases, proteases, and phosphatases. These molecules are essential for nearly all biological functions, including cellular signaling, metabolic regulation, and the maintenance of tissue structure (UniProt, 2024). In the context of pharmacology, this term is considered an "incorrect" or overly generic target designation because it encompasses thousands of distinct proteins rather than a single, specific therapeutic site (IUPHAR/BPS, 2023). Drugs typically interact with the enzymes that modify these substrates—such as protease inhibitors used in viral infections—or consist of the substrates themselves, as seen in hormone replacement therapies like insulin (PubMed, 2022). Because the category is so diverse, it lacks a unified mechanism of action or a specific safety profile. Effective drug development requires the identification of a specific protein or peptide within this group to ensure therapeutic precision and minimize off-target effects. Consequently, while these substrates are vital components of health and disease, they do not constitute a discrete target for drug discovery.

Other names

Polypeptide substratesProteinaceous substratesEnzymatic substratesProteic reactants

As a broad category, these molecules serve as the reactants for various enzymes; therapeutic strategies often involve inhibiting the enzymes that process them or providing synthetic versions of the substrates to restore physiological function.