Fl- Lactamases

Other serine hydrolases such as cholinesterases, carboxylesterases, lipases, and fl-lactamases of classes A, C, and D have a hydrolytic mechanism similar to that of serine peptidases [25-27], The catalytic mechanism also involves an acylation and a deacylation step at a serine residue in the active center (see Fig. 3.3). All serine hydrolases have in common that they are inhibited by covalent attachment of diisopropyl phosphorofluoridate (3.2) to the catalytic serine residue. The catalytic site of esterases and lipases has been less extensively investigated than that of serine peptidases, but much evidence has accumulated that they also contain a catalytic triad composed of serine, histidine, and aspartate or glutamate (Table 3.1). 

Craig, S., Hollecker, M., Creighton, T.E., and Pain, R.H. 1985. Single amino acid mutations block a late step in the folding of fl-lactamase from Staphylococcus aureus. J. Mol. Biol. 185 681-687. 

CH2OCONH2 cefoxitin stable to fl-lactamases and mammalian esterases... 

Lincomycin increased the TEM - 2 fl - lactamase activity of Escherichia Coli (E. Coli) K -12 cells carrying plasmid RP4 at a concentration which slightly inhibited cell growth (70). In a control culture, a lactamase activity reached its maximal level in late log phase, where as when lincomycin was present, a - lactamase activity continued to increase into the stationary phase. Lincomycin (100 pgftnl) inhibited both cell growth and protein synthesis by about 35 % but the activity of stimulated o lactamase was 2.5 fold per ml of culture and about 4 - fold per cell after 20 hours of growth. Inactivation oh b lactamase appeared to be faster when lincomycin was present. This was determined by measuring the decrease ip b lactamase activity when phenethyl alcohol was present to prevent maturation of the enzyme. 

Haginaka, J. Wakai, J. Yasuda, H. Liquid chromatographic assay of fl-lactamase inhibitors in human serum and urine using a hoUow-fiber postcolumn reactor. Anal.Chem., 1987, 59, 324-327 [serum urine post-column reaction]... 

Goessens WHF, van der Bij AK, van Boxtel R, Pitout JDD, van Ulsen P, Melles DC, Tommassen J. Antibiotic trapping by plasmid-encoded CMY-2 fl-lactamase combined with reduced outer membrane permeabihty as a mechanism of carbapenem resistance m Escherichia cob. Antimi-crob Agents Chemother. 2013 57 3941-9. 

Gon9alves A, Poeta P, Monteiro R, Marinho C, Silva N, Guerra A, Petrucci-Fonseca F, Rodrigues J, Torres C, Vitorino R, Domingues P, Igrejas G. Comparative proteomics of an extended spectrum fl-lactamase producing Escherichia coli strain fiom the Iberian wolf. J Proteomics. 2014 104 80 93. 

J. Lamotte-Brasseur, V. Lounnas, X. Raquet, and R. C. Wade, Protein Sci., 8, 404 (1999). pKa Calculations for Class a fl-Lactamases Influence of Substrate Binding. 

One of the prindpal deficiencies of the older cephalosponns was the lack of resistance to -lactamases. Compounds with improved jS-lactamase resistance have one or more of tire following characteristics a second, monovalent substiluenl on the a-carbon of the C-7 acyl group such as is found in cefamandole and cefoperazone a jy -oxime substiluenl, e.g., cefuroxime and ceftriaxone a methoxy, or formamido, substituent on the fl-laclam ring at tire 7 a-position such as in cefoxitin. However, these various substituents have different effects, and increased resistance to one enzyme does not indicate resistance to all (3-lactamases. 

---