Characterization of certain proteinase isoenzymes produced by benign and virulent strains of Bacteroides nodosus.

Three proteinase isoenzymes from one benign strain of Bacteroides nodosus and five proteinase isoenzymes from each of two virulent strains of B. nodosus were purified by horizontal slab polyacrylamide gel electrophoresis. The purified isoenzymes hydrolysed casein, collagen I, collagen III, elastin, alpha-elastin, fibrinogen, gelatin, haemoglobin and alpha-keratin. The pH optima of all the isoenzymes lay between 7.25 and 9.5, the range of 8.75-9.25 being common to all. The isoenzymes were inhibited by phenylmethylsulphonyl fluoride, diphenylcarbamyl chloride, L-(1-tosylamide-2-phenyl)ethyl chloromethyl ketone, EGTA and EDTA, indicating that they were chymotrypsin-like serine proteinases that require a metal ion for stability or activity. EDTA inhibition was not reversed by addition of Ca2+ or Mg2+. Some isoenzymes were activated by Mg2+, Ca2+, Cr3+ and Se4+ and all were inhibited by Fe2+, Co2+, Cu2+, Zn2+, Cd2+ and Hg2+. Isoenzymes from benign strains had a lower temperature stability, losing all activity at 55 degrees C, whereas those from virulent strains lost all activity at 60 degrees C.