A (-)gamma-lactamase, Mhg, from Microbacterium hydrocarbonoxydans was over-expressed in E. coli and was characterized after purification. The maximum activity was at pH 8.0 and 60A degrees C and the half life of Mhg was similar to 30 min at 75A degrees C. The enzyme was activated by DTT. The catalytic triad of the (-)gamma-lactamase is comprised of residues Ser98, Asp230, and His259 and an oxyanion hole was formed by Tyr32 and Met99 according to the alignment results. Under native conditions, the (-)gamma-lactamase consists of two 31 kDa homodimers.