One of the most common way that bacteria become resistant to antibiotics is by the production of metallo-beta-lactamases (M beta Ls) to hydrolyze the beta-lactam-containing antibiotics. In this paper, the thermodynamic parameters of benzylpenicillin hydrolysis with B1 subclasses M beta L CcrA (carbapenem and cephamycin resistance) from Bacteroides fragilis were determined by microcalorimetry. The activation free energy Delta G(not equal)(theta) is 87.90 +/- 0.03, 88.99 +/- 0.01, 89.93 +/- 0.04 and 90.93 +/- 0.05 kJ mol(-1) at 293.15, 298.15, 303.15 and 308.15 K, activation enthalpy Delta H-not equal(theta) is 29.21 +/- 0.03 kJ mol(-1), activation entropy Delta S-not equal(theta) is -200.34 +/- 0.08 J mol(-1) K-1, the reaction order is 1.4, and the apparent activation energy E is 31.71 kJ mol(-1). The thermodynamic characterization indicated that CcrA prefer to hydrolyze penicillins among three kinds of beta-lactam-containing antibiotics. (C) 2013 Elsevier B.V. All rights reserved.