Catalytic peptides are short sequences of amino acids capable of catalyzing a specific chemical reaction. Catalytic peptides are often inspired by enzyme active sites. Enzyme catalytic activity arises from the specific arrangement of amino acid residues within its three-dimensional structure, which allows it to interact with substrates in a precise and selective manner. Catalytic peptides can be utilized as catalysts in organic and inorganic reactions and for asymmetric transformations/chiral catalytic reactions. Short catalytic peptides are characterized by conformational flexibility and can be easily tuned and functionalized numerous ways. Their structure consisting of monomers of amino acids allows countless possibilities in the design of catalytic peptides. Still, the relationship between the amino acid sequence of a peptide and its catalytic activity is not entirely understood. Despite their great potential, they face several challenges, such as low stability and low selectivity. This thesis deals with unraveling the structure–activity relationship of a short catalytic peptide, CG11, and the modification of its structure with the goal to achieve better catalytic efficiency. Cyclization of the linear CG11 peptide serves as a straightforward but powerful modification that offers improved rigidity and stability. With continuing research and development of novel peptides that can be finely tuned for specific functions, catalytic peptides can be employed as highly efficient biocatalysts in chemical and biotechnological industry.