Recent advances in prokaryotic peptide transport

Synthesis and inhibitory activity of 8-substituted 2-deoxy-β-KDO against CMP-KDO synthetase

3-Deoxy-D-manno-octulosonate cytidyltransferase (CMP-KDO synthetase) is involved in the biosynthesis of lipopolysaccharide (LPS) which is an essential component of the outer membrane of gram-negative bacteria. New CMP-KDO synthetase inhibitors, 8-substituted derivatives of 2-deoxy-beta-KDO (2) have been prepared. Compounds 8, 11, 15 and 16 in which the 8-hydroxyl group of 2 is replaced by guanidine, di(carbamoylethyl)amino, p-methoxy- or p-nitro-benzyloxycarbonylamino, respectively affect moderately the CMP-KDO synthetase activity.

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

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)

Utilization of amino acids and peptides by Fusobacterium nucleatum

Fusobacterium nucleatum strains ATCC 10953, Fevl, F1, F3, and F6 utilized amino acids, in particular glutamate, histidine, and aspartate were common to all strains. Strain differences were observed in the utilization of threonine, serine, lysine, tyrosine, and methionine, and only strain ATCC 10953 utilized all these amino acids. The glutamate and histidine pools were in all cases fully depleted before the other amino acids were attacked and at the same time all strains except 10953 started to utilize peptides at a noticeable rate. For strain Fevl, glutamyl- and aspartyl-containing peptides seemed to be of considerable nutritional importance, and this strain did not grow on a medium based on amino acids alone. On the other hand, strain 10953 did not utilize any peptides to a noticeable extent, and it could grow on an amino acid based medium.