Peptide Utilization by Pseudomonas putida and Pseudomonas maltophilia

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Abstract
P. putida assimilates peptides and hydrolyzes them with intracellular peptidases. Amino acid auxotrophs (his, trp, thr or met) grew on a variety of di- and tripeptides up to twice as slowly as with free amino acids. P. putida has separate uptake systems for dipeptides and oligopeptides (3 residues). Although the dipeptide system transported a variety of structurally diverse dipeptides, it did not transport peptides having unprotonatable N-terminal amino groups, blocked C-terminal craboxyl groups, D-residues, .gtoreq. 3 residues, N-methylated peptide bonds or .beta.-amino acids. Oligopeptide uptake lacked amino acid side-chain specificity, required a free N-terminal L-residue and had an upper size limit. Glycylglycyl-D,L-p-fluorophenylalanine inhibited growth of P. putida. Uptake of glycylglycyl [1-14C]alanine was rapid and inhibited by 2,4 dinitrophenol. Dipeptide and oligopeptide uptake were constitutive. Dipeptides competed with oligopeptides for oligopeptide uptake, but oligopeptides did not compete in the dipeptide system. Final bacterial yields were 5-10 times greater when P. putida his was grown on histidyl di- or tripeptides rather than on free histidine, because the histidyl residue was protected from catabolism by L-histidine ammonia-lyase [EC 4.3.1.3]. Methionine peptides satisfied the methionine requirements of P. maltophilia. Generation times on glycylmethionine and glycylmethionylglycine were equal to those obtained with free methionine. Methionylglycylmethionylmethionine gave a generation time twice that of free methionine. Growth of P. maltophilia was inhibited by glycylglycyl-D,L-p-fluorophenylalanine.