Interacting selectively and non-covalently with a drug, any naturally occurring or synthetic substance, other than a nutrient, that, when administered or applied to an organism, affects the structure or functioning of the organism; in particular, any such substance used in the diagnosis, prevention, or treatment of disease.

Interacting selectively and non-covalently with penicillin, any antibiotic that contains the condensed beta-lactamthiazolidine ring system.

Catalysis of the reaction: (Ac)2-L-Lys-D-alanyl-D-alanine + H2O = (Ac)2-L-Lys-D-alanine + D-alanine.

Catalysis of the reaction: (Ac)2-L-Lys-D-alanyl-D-alanine + H2O = (Ac)2-L-Lys-D-alanine + D-alanine.

Catalysis of the reaction: 2 a peptidoglycan dimer (tetrapeptide) + 3 H2O = a peptidoglycan tetramer with L,D cross-links (L-Lys-D-Asn-L-Lys) + di-trans,poly-cis-undecaprenyl diphosphate + 4 D-alanine.

Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).

Catalysis of a biochemical reaction at physiological temperatures. In biologically catalyzed reactions, the reactants are known as substrates, and the catalysts are naturally occurring macromolecular substances known as enzymes. Enzymes possess specific binding sites for substrates, and are usually composed wholly or largely of protein, but RNA that has catalytic activity (ribozyme) is often also regarded as enzymatic.