Chapter VI 



PRODUCTION OF ENZYMES AND OF GROWTH- 

 PROMOTING SUBSTANCES 



Actinomycetes are able to produce a variety of agents which are 

 essential to their own growth or to that of other organisms living in 

 association with them. Some of these substances are of the nature of 

 enzymes, others are vitamin-like substances, and still others are lytic 

 agents. Actinomycetes also produce a varietv of bacteriostatic and 

 bactericidal substances, or antibiotics, which are discussed in Chapter 

 VII. 



Production of Enzymes:— Actinomycetes produce both extracellu- 

 lar and endocellular enzymes. Only very few of these enzymes have 

 been concentrated and studied in detail. The presence of others has 

 only been demonstrated in the culture medium or in the mycelium of 

 the organism. 



Proteases.— The wide distribution of proteolytic enzymes among 

 actinomycetes is indicated by the ability of the organisms to liquefy 

 gelatin with different degrees of rapidity and to attack serum protein, 

 coagulated egg-albumin, casein, and vegetable proteins (442), This 

 property has been utilized for species characterization. In nearly half 

 of the species, especially those belonging to the genus Streptomyces, 

 gelatin liquefaction is accompanied by production of a brown pigment. 

 Optimum gelatin liquefaction occurs at a fH of 6.5 to 8.5. Greater 

 acidity is more injurious to the proteolytic process than is a more alkaline 

 reaction. 



The proteolytic action of actinomycetes, in contrast with that of 

 fungi and bacteria, is not influenced to any great degree bv the presence 

 of glucose or other available carbohydrates. Tlie breakdown of the 

 protein proceeds, through the amino acid stage, to ammonia. This is 

 brought out in Table 18. In some cases it is easy to establish the in- 

 termediary formation of peptides and amino acids; in other cases, it is 

 more difficult. 



The proteolytic enzymes are fairly resistant to the effect of tempera- 

 ture, since they are able to withstand heating at 70° C. for 30 minutes. 

 According to Lieske, the resistance of the enzvmes to the eff'ect of 

 higher temperature is greater than that of the living cells of the or- 

 ganisms, the latter being killed at 62°-65°C. When the enzymes are 



