= Lysozyme
{wiki}
<Lysozyme> is a <protein> <enzyme> that attacks the <peptidoglycan> of bacterial <cell walls>. Its <active site> is a cleft in the folded <protein structure>, where a suitable <substrate> can interact with positioned chemical groups. This illustrates why possessing the right <amino acid residues> is insufficient if their spatial arrangement is lost. See https://www.ncbi.nlm.nih.gov/books/NBK26911/[Alberts et al.: lysozyme as a worked example of protein binding and enzyme function].
A concrete structural example is Cheetham, Artymiuk and Phillips's 1992 study of hen egg-white <lysozyme> bound to a short <carbohydrate> that inhibits its action. The bound <carbohydrate> occupies part of the <active site>; it is not a reacting <substrate> in this complex. The study describes specific interactions and changes of shape accompanying binding. Thus a real binding site has chemical interactions and flexibility as well as a geometric outline. See https://pubmed.ncbi.nlm.nih.gov/1569548/[Cheetham, Artymiuk and Phillips, 1992: structure of a lysozyme complex with bound inhibitor] and https://www.rcsb.org/structure/1HEW[RCSB PDB entry 1HEW: the authors' structure and bound three-unit carbohydrate]. The diagrams above illustrate the idea; their twelve-residue strings are not <lysozyme> sequences or coordinates.
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