TABLE 3.

Kinetic constants determined with purified CTX-M enzymesa

EnzymePenicillin GAmoxicillinTicarcillinPiperacillinCephalothinCefuroximeCefoxitineCefotaximeCefpiromeCefepimeCeftazidimeAztreonam
kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)kcat (s−1)Km (μM)
CTX-M-119011871015122,45011515075112b317125516270150b
CTX-M-32702.51601854029180662,80096349<0.01380113303160.2170<0.01>3,000190188
CTX-M-5230501,500c350c0.410.18210957.444021730
CTX-M-8150115512171474191,6008735125b72744551,2001449902>50013800
CTX-M-92952590206035110203,00015035050450120950800260010220
CTX-M-1429020100204524200482,700175320404151309401,000361010200
CTX-M-1830291010531715237c216c4070NDdND20546565020525NDND2286
Toho-23.661021214e18e1308412,000470<0.14.8220661.31600.1140
CTX-M-154010203825351335437013<0.0115054120195101,07521,7601.511
CTX-M-16656401010134582,80083500451,40015084052015350317
CTX-M-27116510113982328379451131506352033300.417
CTX-M-19515110013081030c123c840NDND360NDNDNDND0.0225NDND
  • a Data are from references 8, 14, 15, 16, 20, 36, 55, 73, and 77.

  • b Km determined as Ki by substrate competition.

  • c Kinetic constant for cephaloridine.

  • d ND, not determinable.

  • e Kinetic constant for carbenicillin.