342 BACTERIOLOGICAL CHEMISTRY 



of atmospheric nitrogen. When amino -acids are avail- 

 able, as ordinarily occurs when bacteria grow under normal 

 conditions in normal nutrient media it is very probable 

 that proteins are built up by the reversal of the action of 

 proteolytic enzymes. Bergmann has shown, for instance, 

 that papain will convert a mixture of benzoylglycine and 

 aniline into benzoylglycine anilide : — 



CsHg.CO.NH.CHa.COOH + CeHs.NHa > 



CeHg.CO.NH.CHa.CO.NH.CeHg 4- HaO 



although under the same conditions it hydrolyses ben- 

 zoylglycine amide to benzoylglycine and ammonia : — 

 C6H5CO.NH.CH2.CONH2 + H2O > CeHs.CO.NH.CHa.COOH + NH3 



Papain, in addition to the above reactions, also catalyses 

 conversion reactions ; for instance it converts a mixture 

 of benzoylglycine amide and aniline into benzoylglycine 

 anilide and ammonia : — 



C6H5.CO.NH.CH2.CO.NH.CeH4 + NH3 



Bergmann pictures the in vivo synthesis of proteins as 

 consisting of the action of a specific enzyme breaking 

 down, synthesising and rearranging a number of peptide 

 fragments until a protein is formed which is stable in 

 the presence of the enzyme . The particular protein formed 

 will depend on the fragments available and on the 

 specificity of the enzyme. In any one organism or cell 

 several enzymes may be present, resulting in the forma- 

 tion of a corresponding number of different proteins. 



The proteinases are, in all probability, proteins 

 themselves or at least contain protein constituents. 

 It must be assumed, therefore, that there are proteins 

 which are capable of multiplication or autocatalysis. 

 Apart from the enzymes such autocatalytic proteins 

 are to be found in the crystalline viruses and in the 

 desoxyribonucleic acids responsible for the conversion of 

 Rough pneumococci to Smooth organisms (see p. 337). 



'A i-ecently developed method wJiicJi promises to be 



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