Peptostreptococcus micros has a uniquely high capacity to form hydrogen sulfide from glutathione

Abstract

There are high amounts of hydrogen sulfide in deep periodontal pockets. This volatile sulfur compound may be formed from L-cysteine, but only low levels of this amino acid can be expected to be present in periodontal pockets. Glutathione, L-gamma-glutamyl-L-cysteinylglycine, is in high concentration in most tissue cells, and this tripeptide may be more readily available as a source of hydrogen sulfide formation in the pockets. The ability of 37 different species of oral bacteria to utilize glutathione in hydrogen sulfide formation was studied. Of these species, only 2 species of Peptostreptococcus and 5 species of Fusobacterium formed high amounts of hydrogen sulfide from glutathione within 24 h. Since the initial rate of hydrogen sulfide formation was more than 5 times higher in Peptostreptococcus micros than in any of the other bacterial species, the kinetics of sulfide formation from glutathione by P. micros was further elucidated. The formation of sulfide followed quite closely hyperbolic Michaelis-Menten kinetics. The maximal initial rate of sulfide formation (Vmax) was 163 +/- 2 nmol sulfide per minute per milligram of cellular protein. Half maximal initial rate (Km) was obtained at 7.4 +/- 0.8 microM glutathione. The initial rate of sulfide formation from L-cysteine was much slower and was almost proportional to L-cysteine concentration. This difference in kinetics of sulfide formation between glutathione and L-cysteine strongly suggested that glutathione was actively transported into the cell, whereas the transport of L-cysteine was more or less controlled by diffusion. The sulfide formation from the dipeptide L-cysteinylglycine also followed quite closely hyperbolic Michaelis-Menten kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of Glutathione Metabolism of Treponema denticola in Bacterial Growth and Virulence Expression

“…High levels of H 2 S (up to 2 mM) have been detected in infected periodontal pockets, while low levels have been detected in clinically healthy sites (22,34,36,42). In vitro, H 2 S has been shown to be cytotoxic for a variety of host cells, including gingival fibroblasts and epithelial cells (4, 10, 40, 48).Several reports have described H 2 S formation from metabolism of human serum proteins, cysteine, and glutathione by oral bacteria (6,37,38). Despite these observations, the metabolic pathways leading to H 2 S production from glutathione by oral bacteria have not been delineated.…”

Oxidative Injury and Inflammatory Periodontal Diseases : the Challenge of Anti-Oxidants to Free Radicals and Reactive Oxygen Species

“…The lowered GSH levels found in PE do not necessarily imply its involvement in anti-oxidant activity, since its -SH may simply have been used by oral bacteria to form hydrogen sulfide (Carlsson et al, 1993;Tang-Larsen et al, 1995). However, whatever the reason for -SH reduction, the result is a lowered overall anti-oxidant potential of the periodontium.…”

Exogenous Glutathione Completes the Defense against Oxidative Stress in Haemophilus influenzae

“…In contrast, the thiol tripeptide is absent from gram-positive bacteria, with the exception of some members of the BacillusClostridium group (8,36,68). For that group however, it was shown that the GSH present in these cells was most often not the result of intrinsic biosynthesis but was acquired by import of a reducible form of GSH from the growth medium.…”