|Gene:||blaP1a||Accession Number: G-10219 (MetaCyc)|
Species: Pseudomonas aeruginosa
Bacterial β-lactamse enzymes hydrolyze the peptide bond in the β-lactam ring of β-lactam antibiotics, providing a mechanism of antibiotic resistance. Antibiotic resistant bacteria remain a major world health problem. Bacterial resistance to β-lactam antibiotics can also involve alterations in penicillin binding proteins and reduced antibiotic permeation across the membrane. The problem is further compounded by β-lactamase gene transfer among bacterial species and the development of resistance to β-lactamase inhibitors such as clavulanate.
Hundreds of bacterial β-lactamase enzymes have been characterized functionally and structurally using both experimental and computational methods, and many crystal structures have been determined. These enzymes have been classified into different groups, subgroups and classes. The nomenclature of individual enzymes, however, remains without convention [Garau05], [Jacoby06] and reviewed in [Majiduddin02].
β-Lactamase classes A, B, C and D are based on amino acid sequence similarity and catalytic mechanism. Class A, C and D enzymes contain an active site serine. Class B enzymes are metallo-β-lactamases, requiring primarily Zn2+ for catalysis. Genes encoding class D enzymes are found predominantly on plasmids (reviewed in [Majiduddin02]). Some examples are class A (this enzyme) , class B carbapenemase and class C β-lactamase; penicillin resistance.
PSE-4 β-lactamase is a class A β-lactamase. This class is found in both Gram-positive and Gram-negative bacteria. The structural motifs and catalytic mechanism of class A enzymes have been reviewed [Majiduddin02]. This enzyme from Pseudomonas aeruginosa has been identified [Newsom70] and characterized [Furth75] and its crystal structure has been determined [Lim01].
The apparent molecular mass of the enzyme was determined by gel filtration chromatography [Furth75].
Gene Citations: [Partridge02]
Locations: periplasmic space
Molecular Weight of Polypeptide: 31.406 kD (from nucleotide sequence), 32.0 kD (experimental) [Furth75 ]
Relationship Links: Entrez-Nucleotide:PART-OF:AF313471 , InterPro:IN-FAMILY:IPR000871 , InterPro:IN-FAMILY:IPR012338 , InterPro:IN-FAMILY:IPR023650 , PDB:Structure:1g68 , Pfam:IN-FAMILY:PF00144 , Prints:IN-FAMILY:PR00118 , Prosite:IN-FAMILY:PS00146
|Cellular Component:||GO:0030288 - outer membrane-bounded periplasmic space [Furth75]|
Enzymatic reaction of: PSE-4 β-lactamase
EC Number: 22.214.171.124
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
The reaction is favored in the direction shown.
Alternative Substrates for a β-lactam: phenoxypropylpenicillin [Furth75 ] , cephalothin [Furth75 ] , cephalosporin 87/312 [Furth75 ] , cephalexin [Furth75 ] , cephaloridine [Furth75 ] , cloxacillin [Furth75 ] , dicloxacillin [Furth75 ] , oxacillin [Furth75 ] , penicillin V [Furth75 ] , phenoxyethylpenicillin [Furth75 ] , carbenicillin [Furth75 ] , α-sulfobenzylpenicillin [Furth75 ] , methicillin [Furth75 ] , penicillin G [Furth75 ] , penicillin N [Furth75 ] , cephalosporin-C [Furth75 ]
This enzyme hydrolyzes a variety of β-lactam substrates as shown above. In general, penicillins were hydrolyzed more rapidly than cephalosporins and the Km values were lower for penicillins. However, the penicillins oxacillin, cloxacillin and dicloxacillin. were hydrolyzed slowly. It did not hydrolyze 6-epibenzylpenicillin. The hydrolysis of penicillin G was not inhibited by EDTA or p-chloromercuribenzoate. The enzyme showed substrate inhibition with cloxacillin and cephaloridine. penicillin G protected the enzyme against cloxacillin inhibition [Furth75].
pH(opt): 8.0 [Furth75]
Lim01: Lim D, Sanschagrin F, Passmore L, De Castro L, Levesque RC, Strynadka NC (2001). "Insights into the molecular basis for the carbenicillinase activity of PSE-4 beta-lactamase from crystallographic and kinetic studies." Biochemistry 40(2);395-402. PMID: 11148033
Newsom70: Newsom SW, Sykes RB, Richmond MH (1970). "Detection of a beta-lactamase markedly active against carbenicillin in a strain of Pseudomonas aeruginosa." J Bacteriol 101(3);1079-80. PMID: 4985588
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