FIG. 6.

Effects of recombinant GGT and its inhibitor GNA on glutathione utilization in P. gingivalis. P. gingivalis W83 was incubated without (No addition) or with 2 mM l-cysteine, Cys-Gly, or glutathione. GGT was added at 2 μg/ml (GGT + GSH), and GNA was added at 16 mM (GNA + GGT + GSH). P. gingivalis was able to metabolize l-cysteine and Cys-Gly, but not glutathione, to produce significant amounts of H₂S and ammonia. The addition of GGT enhanced the bacterial capacity for metabolizing glutathione. The effect of GGT was ameliorated by the presence of GNA. The bars represent means plus standard deviations; n = 3.