Table 2.

Kinetics of nitrocefin and prodrug hydrolysis by β-lactamase and β-lactamase variant

ProteinSubstratekcat (s−1)Km (μmol/L)kcat/Km (mol/L−1 s−1)
β-LactamaseNitrocefin359 ± 1613.8 ± 2.32.6 × 107
β-Lactamase variantNitrocefin272 ± 1715.7 ± 4.11.7 × 107
β-LactamaseCephalosporin-melphalan904 ± 124294 ± 213.0 × 106
β-Lactamase variantCephalosporin-melphalan656 ± 36336 ± 612.0 × 106