Il8 NITROGEN METABOLISM 



left the connective tissue intact [34, 15]. The collagenase of 

 CI. welchii type A, also known as the kappa (k) toxin, has 

 been purified considerably [11]. Although on a weight basis 

 this material was less toxic than the lecithinase (a-toxin) of 

 CI. welchii, it was ten to fifty times more toxic than the 

 endotoxins of Gram-negative bacteria. A curious feature of 

 the purified collagenase is that after exposure to mild alkali 

 or to heat, it still attacked gelatin but not collagen [9]. This 

 treatment may have altered the structure of the enzyme such 

 that it can combine only with gelatin, and this may also be 

 the reason why there is a change in the optimum pH for 

 gelatinase activity. Another possible, though perhaps un- 

 likely, explanation is that exposure to heat or alkali de- 

 natured the collagenase and at the same time activated a 

 specific gelatinase precursor [9]. Some confusion exists in 

 the naming of the enzymes which attack gelatin and collagen 

 and it is sometimes assumed that the terms gelatinase and 

 collagenase are synonymous. However, Evans and Wardlaw 

 have evidence that though the formation of collagenase by 

 various species of bacilli is always accompanied by gelatinase 

 activity, some organisms, e.g. B. subtilis, produce a gelatinase 

 and yet have no apparent action on collagen [16]. 



Other proteinases of the Clostridia 



Apart from the specific gelatinase, Maschmann found 

 three other types of proteolytic enzymes in various bacterial 

 culture filtrates (Table 8.1). One type was active against pro- 

 teins and peptones, and like the specific gelatinase, was found 

 in young as well as old cultures and activity was unaffected 

 by the presence of Og: gelatin was also digested, but usually 

 not as rapidly as casein. The two other types of proteases, 

 one active against proteins, the other against peptides, ap- 

 peared in the medium after the cultures had stopped grow- 

 ing, and it is therefore possible that at least in some instances 

 they were intracellular enzymes released by autolysis. Their 

 activity was depressed by O2 and was only maximal in the 

 presence of reducing substances (HgS, cysteine or gluta- 

 thione) whilst in addition, the peptidases also required di- 

 valent cations (Mg+"^, Fe++ or Mn++). The Og-labile 



