Transport and hydrolysis of peptides by microorganisms.

The structural specificities of the dipeptide and oligopeptide permeases of E. coli are briefly reviewed and related to the requirements found for other microorganisms. New, quick, sensitive methods for studying peptide transport are described, based on the following: (i) peptide-dependent incorporation of free radioactive amino acid into newly synthesized protein by a double amino acid auxotroph, (ii) colorimetric assay of peptide-dependent enzyme synthesis by an amino acid auxotroph, (iii) dansyl fingerprint technique. These approaches provide information on peptide binding affinity to a permease and rates of peptide uptake and amino acid efflux. Among current and future research areas considered are: the influence of the pKb of the N-terminal amino group on transport, generality of peptide transport in microorganisms, energy coupling and regulation, involvement of binding proteins, and the 'smugglin' concept. Peptide hydrolysis, and nutritional ultilization of peptides, by microorganisms are briefly discussed.