KARL MEYER 



The protective action of lysozyme, however, is strongly sug- 

 gested in vitamin A deficiency. Thus Findlay (12) reported a cure 

 of the xerophthalmic condition in vitamin A deficient rats by washing 

 the eyes with human tears. Andersen (3) found a subnormal amount 

 of lysozyme in the tears of human twins suffering from xerophthalmia; 

 on addition of vitamin A to the diet of the twins, the lysozyme increased 

 and the xerophthalmia concurrently improved. A renewed study of 

 nutritional factors in the production and activity of lysozyme seems 

 indicated. 



The occurrence of lysozyme and lysozyme-like enzymes in many 

 microbes may be interpreted to mean that these enzymes are involved 

 in some metabolic process connected with the carbohydrate substrates 

 in the bacterial membranes. Since some of these membranes, as in 

 M. lysodeikticus, are extremely tough structures, they may serve in 

 facilitating the softening of the membrane in bacterial division. It 

 seems useful also to assume a metabolic role for lysozyme in the animal 

 body. Such a hypothesis would presuppose the occurrence of the 

 substrate of lysozyme in the animal organism and thus far the ocurrence 

 of such a substrate has been reported for egg white only (31). A study 

 of the chemical specificity of lysozyme undoubtedly will be useful in 

 establishing the presence or absence of such substrates in the animal 

 body. 



The susceptible organisms become highly resistant to lysozyme 

 action when grown in the presence of sublethal doses of the enzyme. 

 It will be intei'esting to investigate this adaptation to determine whether 

 the adapted organism fails to produce the substrate of lysozyme at all, 

 or whether the adaptation is due to a chemical modification of the 

 membrane polysaccharide so that it no longer is attacked by lysozyme. 



Recently, attention was called to the similarity in occurrence 

 and chemical properties of lysozyme and avidin, the protein which 

 neutralizes the vitamin biotin (22). Avidin and lysozyme are both 

 found in egg white, in the oviduct of birds, and in fish eggs; both are 

 basic proteins, very stable toward acid and unstable toward oxidation 

 and alkaline reaction. They undoubtedly are not identical, either 

 in respect to their chemical or biological properties, the main chemical 

 difference between the two being that of solubility, for lysozyme is a 

 very soluble, and avidin is a highly insoluble, protein, even at acid 

 pH values. They differ in their biological activity in that freshly 



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