Helicobacter pylori and proteolytic activity.

Protease activity of 10 different H. pylori strains, purified marker proteases and protease-positive reference bacteria (Klebsiella ozaenae, Serratia marcescens) were tested against bovine haemoglobin, porcine mucin, bovine serum albumin, gelatin and casein as substrates. After incubation in development buffer and subsequent staining with Coomassie blue, protease activity bands were demonstrated as transparent spots after polyacrylamide gel electrophoresis (PAGE) on gels with incorporated substrate. Presence of protease activity was investigated in a wide pH range (pH 2.0-9.0). Although marker proteases (0.15-0.2 microgram per slot) as well as protease-positive bacteria (2-30 micrograms per slot) clearly showed proteolytic activity in gels containing 0.1-0.2% protein mL-1, no proteolytic activity was demonstrated in any of the H. pylori strains tested. This finding indicates that H. pylori does not possess significant protease activity, as this would have been detected by this sensitive method.