title: Utilization of D-phenylglycyl-glycine in Escherichia coli.
abstract: Escherichia coli K 12 is able to utilize the dipeptide D-phenylglycyl-glycine as a source of glycine. Growth experiments with a glycine auxotrophic mutant show that utilization of there dipeptide is competitively inhibited by D-alanine at a Ki of 4 x 10(-4) M. In contrast, L-alanyl-L-alanine which is transported via the system specific for dipeptides does not interfere with the utilization of D-phenylglycyl-glycine. This indicates that the dipeptide is hydrolyzed prior to uptake, and D-alanine therefore competes with the uptake of glycine via the transport system common for both amino acids. This was confirmed by examining the growth response of various transport mutants. A mutant deficient in the transport of oligo- and dipeptides grows as well as the wild type on D-phenylglycyl-glycine, whereas the growth of mutants deficient in the transport of glycine is severely impaired or prevented with this dipeptide. It is therefore demonstrated that D-phenylglycyl-glycine is hydrolyzed prior to uptake. This is a mechanism of peptide utilization in E. coli K 12 which is distinct from that described so far for other dipeptides.
mesh_terms: D000409:Alanine / Q000494:pharmacology; D001692:Biological Transport; D004151:Dipeptides / Q000378:metabolism* / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism*; D006033:Glycylglycine / Q000031:analogs & derivatives / Q000378:metabolism*; D009154:Mutation; D013237:Stereoisomerism
chemical_list: D004151:Dipeptides; D006033:Glycylglycine; C002956:alanylalanine; C027914:phenylglycylglycine; D000409:Alanine