Investigation of the types and characteristics of the proteolytic enzymes formed by diverse strains of Proteus species

Many diverse clinical isolates of Proteus mirabilis (48 strains), E. penner i (25), P. vulgaris biogroup 2 (48) and P. vulgaris biogroup 3 (21) from ma n were examined for their ability to produce proteolytic enzymes and the na ture and characteristics of the proteases were studied. All the P. penneri isolates, most (94-90%) of the P. mirabilis and P. vulgaris biogroup 2 isol ates, but only 71% of the P. vulgaris biogroup 3 isolates, secreted proteol ytic enzymes. These were detected most readily at pH 8 with gelatin as subs trate. A strong correlation was found between the ability of a strain to fo rm swarming growth and its ability to secrete proteases. Non-swarming isola tes invariably appeared to be non-proteolytic. However, some isolates, part icularly of P. vulgaris biogroup 3, were non-proteolytic even when they for med swarming growth. Analysis of the secreted enzymes of the different Prot eus spp. on polyacrylamide-gelatin gels under various constraints of pH and other factors showed that they were all EDTA-sensitive metalloproteinases. Analysis of the kinetics of production of the proteases revealed the forma tion of an additional protease of undefined type and function that was cell -associated and formed before the others were secreted. The secreted protea se was subsequently modified to two isoforms whose mass (53-46 kDa) varied with the Proteus spp. and the strain. There was no evidence that the secret ed proteases of strains of Proteus spp. were of types other than metallopro teinases.