PROTEOLYTIC ENZYMES I23 



Infection with Strep, haemolyticus soon results in the forma- 

 tion of an antibody which completely antagonizes strepto- 

 kinase. 



Peptidases of bacteria, aspergilli and yeast [4, 25, 36] 



A number of observations have provided evidence for the 

 occurrence of peptidases in micro-organisms similar to those 

 in animals and plants, and in general their activity has been 

 studied using simple substrates, di- and tri-peptides of 

 glycine, alanine and leucine. Many, but not all, of these 

 enzymes are activated either by thiol compounds or by di- 

 valent cations: some require both types of activator (Table 

 8.2). The peptidases of the Clostridia exhibit poor activity 



TABLE 8.2 



ACTIVATION OF MICROBIAL PEPTIDASES 



The activators listed below are those which have been found to 

 increase the activity of various preparations of peptidases from the 

 organisms shown in the table. Which of these substances are the 

 most effective activators for particular enzyme preparations de- 

 pends on the peptidase concerned and sometimes on the substrate 

 being tested. 



Organism Activators 



Aspergillus parasiticus Zn , cysteine 



Bacillus megatherium Zn , Mn , Fe , cysteine 



Clostridiu?n histolyticum Mn , Fe , cysteine 



Escherichia coli Mg"^"*", Mn"^"^ 



Leuconostoc mesenteroides TjXi , Mn , Cd , Pb , cysteine 



Phytomonas tumifaciens Mg"^"*") Mn , cysteine 



Proteus vulgaris Mg""""*", Mn"*"*" 



Pseudomonas fluorescens Mg > Mn "^ 



Saccharomyces cerevisiae Zn"*" , Mn , Fe , Cl~, Br", NO7 



except in the presence of cysteine together with a cation such 

 as Fe"*"^ or Mn"*"*" (concentrations of the order io~^ to 

 io~^ M.). For the hydrolysis of leucyl peptides, the best acti- 

 vator was Fe"*"^, for alanyl peptides, Mn"'"'' was better [29]. 

 Maschmann suggested that the active enzyme was formed 

 by combination of the cation wdth the reduced form of the 



