[摘要]：In an effort to determine the physiological role of Arabidopsis thaliana Glx2-1, we attempted to uncover a substrate for the enzyme. Glx2-1 did not effectively process 192 diverse substrates found in a commercial screen used for microorganism identification or exhibit arylsulfatase, lactonase, or phosphotriesterase activities. However, Glx2-1 does exhibit beta-lactamase activity with k(cat)/K-M values from 10(3) to 10(5) M-1 s(-1). Glx2-1 can hydrolyze cephalosporins and carbapenems, albeit with rate constants slower than those of most metallo-beta-lactamases. The potential role of a beta-lactamase in the mitochondria of plant cells is briefly discussed.
