Catalytic triad: A catalytic triad refers to the three amino acid residues that function together at the centre of the active site of some hydrolase and transferase enzymes (e.g. proteases, amidases, esterases, acylases, lipases and β-lactamases). An Acid-Base-Nucleophile triad is a common motif for generating a nucleophilic residue for covalent catalysis. The residues form a charge-relay network to polarise and activate the nucleophile, which attacks the substrate, forming a covalent intermediate which is then hydrolysed to regenerate free enzyme. The nucleophile is most commonly a serine or cysteine amino acid, but occasionally threonine. Because enzymes fold into complex three-dimensional structures, the residues of a catalytic triad can be far from each other along the amino-acid sequence (primary structure), however, they are brought close together in the final fold.Extended-spectrum penicillin: The extended-spectrum penicillins are a group of antibiotics that have the widest antibacterial spectrum of all penicillins.Comprehensive Pharmacy Review, Leon Shargel, 6th edition, p917 Some sources identify them with antipseudomonal penicillins,Elsevier's Integrated Review Pharmacology, By Mark Kester, Kelly Dowhower Karpa, Kent E.CHAP domain: In molecular biology, the CHAP domain is a region between 110 and 140 amino acids that is found in proteins from bacteria, bacteriophages, archaea and eukaryotes of the Trypanosomidae family. The domain is named after the acronym cysteine, histidine-dependent amidohydrolases/peptidases.BenzylpenicillinPropicillinVanY protein domain: In molecular biology, VanY are protein domains found in enzymes named metallopeptidases. They are vital to bacterial cell wall synthesis and antibiotic resistance.Specificity constant: In the field of biochemistry, the specificity constant (also called kinetic efficiency or k_{cat}/K_{M}), is a measure of how efficiently an enzyme converts substrates into products. A comparison of specificity constants can also be used as a measure of the preference of an enzyme for different substrates (i.List of strains of Escherichia coli: Escherichia coli is a well studied bacterium that was first identified by Theodor Escherich, after whom it was later named.Procaine benzylpenicillinBenzathine benzylpenicillin