Influence of Hydrophobicity on Oligopeptide Utilization by Oral Streptococci

Abstract

The growth responses of Streptococcus mutans VA-29R, Streptococcus sanguis ATCC 10556, and Streptococcus mitior NIH to hydrophilic and hydrophobic peptides obtained following isopropanol fractionation of Trypticase were compared. Although the two fractions contained peptides of similar molecular size, differences were observed with respect to amino acid compositions. S. mutans VA-29R showed a pronounced difference in growth response to hydrophilic vs. hydrophobic peptides. While growth of this micro-organism on hydrophilic peptides was indistinguishable from that on unfractionated Trypticase, only very slow growth occurred on the hydrophobic peptides. S. sanguis ATCC 10556 and S. mitior NIH also displayed some selectivity, as evidenced by their faster relative growth rates on hydrophilic, as compared with hydrophobic, peptides. The results of this study support the conclusion that the properties of the substrate, as defined by its amino acid composition, may be more important than molecular size as a factor influencing recognition and subsequent utilization of oligopeptides as sources of amino acids for growth by these three oral streptococci.

Saliva-Bacterium Interactions in Oral Microbial Ecology

“…More recent studies extended these findings by demonstrating that the utilization of salivary peptides may be more dependent on their physical properties (hydrophobicity) than their size. That is, hy-drophilic peptides stimulated growth of streptococci far better than hydrophobic peptides (Cowman and Baron, 1990).…”

SO-LAAO, a Novell-Amino Acid Oxidase That EnablesStreptococcus oligofermentansTo OutcompeteStreptococcus mutansby Generating H2O2from Peptone

“…Therefore, lox can play the predominant role in H 2 O 2 formation by S. oligofermentans when lactate is abundant. However, oral saliva is also in rich in polypeptides (39), and oral streptococci take up salivary oligopeptides and then degrade them into free amino acids by intracellular aminopeptidase (2,6,7). Aminopeptidase activity has been detected in S. oligofermentans (data not shown), implying that it might follow a path similar to that of other oral streptococci to obtain amino acids from the environment.…”

Extracellular Arginine Aminopeptidase from Streptococcus gordonii FSS2

“…The utilization of the amino acid is then prioritized, so the transport and metabolism of arginine-containing peptides may become particularly important. The amino acid and peptide transport systems of viridans streptococci have been described previously (2,5,10,25,31), and it has been shown that amino acids and small peptides are readily imported while those exceeding size limitations require hydrolysis by endo-and exopeptidases either present on the surface or secreted by these cells (6). One such activity that could meet the transport and metabolic challenges in vivo is an arginine aminopeptidase.…”