Enzyme

Enzymes are biological macromolecules, predominantly proteins, that catalyse specific chemical reactions by lowering the activation energy required for the reaction to proceed. They exhibit remarkable specificity, with each enzyme typically acting on a particular substrate determined by its three-dimensional active-site geometry. Enzymes are central to peptide biology in multiple ways: proteolytic enzymes (proteases like DPP-4, neprilysin) rapidly degrade circulating peptides, which is why modifications to extend peptide half-life are critical; metabolic enzymes like PARPs and sirtuins require NAD+ as a cofactor; and many peptide effects are mediated through regulation of enzyme activity. For example, GHK-Cu modulates matrix metalloproteinase (MMP) activity to remodel damaged extracellular matrix, and BPC-157 influences nitric oxide synthase activity to support vascular repair.