Enzyme functionalization designates the deliberate covalent attachment of chemical moieties or non-natural functional groups to an enzyme molecule in order to introduce, modulate, or expand its catalytic and physicochemical properties ^[1]. The process operates through bioconjugation chemistries that target reactive side-chain functionalities of amino acid residues, yielding enzyme derivatives bearing new chemical handles, altered surface characteristics, or appended molecular modules ^[1]. Functionalization strategies range from the conjugation of synthetic polymers—such as poly(ethylene glycol)—to the enzyme surface, which imparts stability and novel functionalities, to the site-specific incorporation of noncanonical amino acids via genetic code expansion, which installs chemically orthogonal groups capable of participating in abiotic catalytic mechanisms or post-translational bioorthogonal ligation ^[2][3]. A defining feature of enzyme functionalization is that the modification is directed at the enzyme molecule itself, either prior to or following its association with a solid support, and serves to endow the biocatalyst with capabilities beyond those encoded by the twenty canonical amino acids ^[1][3][4]. The functionalized enzyme is characterized by a covalent linkage between the protein scaffold and the introduced functionality, producing a hybrid biocatalyst whose catalytic activity, substrate scope, selectivity, or operational stability reflects the contribution of the appended chemical module ^[2][3].