KARL MEYER 



This essay will deal with some of the problems connected with muco- 

 lytic enzymes and their substrates. 



Lysozyme 



Lysozyme is a bacteriolytic enzyme which effects the lysis of 

 some microorganisms, notably micrococci and sarcinae. Fleming 

 (13) recognized the wide distribution of this agent in nasal secretion, 

 saliva, tears, leucocytes, and egg white. It also occurs in some micro- 

 organisms in appreciable concentration, as in some molds (18), and 

 in a strain of Sarcina and in a white staphylococcus {S. muscae), both 

 of which are susceptible to lysis by lysozyme obtained from egg white 

 (40). The highest concentration of lysozyme is found in egg white, 

 although calculation on the basis of total protein shows that human 

 tears actually have a higher concentration of the enzyme than does 

 egg white. 



Lysozyme is a basic protein of a molecular weight of about 

 18,000, quite stable toward heat and acid reaction, but relatively un- 

 stable toward oxidation and alkali (33). It was first obtained in 

 crystalline form by Abraham and Robinson (1). Recently an im- 

 prov^ed method for its preparation and crystallization was reported 

 (2). The biological activities of amorphous and crystalline lysozyme 

 are identical, as are the activities of lysozyme prepared by our method 

 and that of the California group. This activity is measured by ob- 

 serving the extent of clearing of a suspension of a susceptible test organ- 

 ism, either visually or photoelectrically. The test organism most 

 widely used is Micrococcus lysodeikticus, which was isolated from the air 

 by Fleming. This micrococcus is more susceptible than other organ- 

 isms, although a strain of Sarcina lutea has been found by Df . Rose 

 Feiner (unpublished) which is as susceptible as A/, lysodeikticus. Most 

 strains of sarcinae, however, have a susceptibility markedly less than 

 that of M. lysodeikticus. 



Lysis by lysozyme does not take place at an acid pYi, although 

 the microorganisms have been shown to be killed by the enzyme at 

 such a/>H. When the /jH is raised to neutral, visible lysis takes place, 

 but this process is independent of the presence of lysozyme. In fact, 

 the optimum pW for the action of lysozyme is in the acid region {'^pH 

 4.5). Some susceptible microorganisms are not lysed at all by lyso- 



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