Peptidase profiles of Pseudomonas fluorescens: identification and properties.

The cell-associated peptidase profiles of 12 strains of Pseudomonas fluorescens (ATCC 948 and 11 related biotypes) were examined. Employing Analytab system API ZYM, a general, strong peptidase activity was detected using L-lysyl-, L-pyrrolidonyl-, L-arginyl-, L-alanyl-, and glycyl-glycyl-beta-naphthylamides as substrates. Conversely, L-tyrosyl-, L-phenylalanyl-, L-histidyl-, L-prolyl-, gamma-L-glutamyl-beta-naphthylamides substrates were hydrolyzed by only a few strains. The peptidases were active, therefore, on substrates responsible for the bitter taste in dairy products. Properties of hydrolytic systems showed no significant changes in the enzymatic profiles when cells were grown on different fermentation media. Enzyme activity was relatively stable during refrigerated (5 degrees C) and frozen (-18 degrees C) storage. The peptidases of P. fluorescens ATCC 948, considered as reference, and strain 22 were identified on Pro-beta-naphthylamides by Michaelis constant values of .528 and .394 mM, respectively, and by different optimal pH and temperature activity on Leu- and Pro-beta-naphthylamides. The peptidase activity on Gly-Phe-beta-naphthylamide in P. fluorescens 30 had optimal values at pH 7.50 and 45 degrees C. These results confirm the relations defined in the enzymatic identification phase and suggest the presence of any analogous peptidases in the biovars of P. fluorescens considered.