116 THE PHYSIOLOGY OF EARTHWORMS 



is found, but by synthesizing lombricine from serine it is noted that 

 the D form is present in this molecule. D-amino-acid oxidase is 

 without effect on natural lombricine, DL-lombricine and synthetic 

 amino-ethyl-seryl-phospho-di-ester prepared from L-serine. This 

 appears to be the first authentic report of a D-amino-acid to be found 

 in animal tissues. 



SEP has also been prepared pure from earthworms and contains 

 serine possessing the d configuration. This is supporting evidence 

 for the suggestion that it is the immediate precursor of lombricine 

 (Ennor et al, 1960). 



The biosynthesis of lombricine in Megascolida cameroni has 

 been elucidated using radioactive labelled materials. It is found 

 that part of the molecule is derived from arginine, part from 

 ethanolamine and part from serine. L-amidino-^^C arginine 

 included in the diet of M. cameroni leads to a high activity in the 

 guanidinoethanol moeity of lombricine whilst SEP remains 

 almost unaffected, indicating that at least one carbon atom in 

 lombricine originates from arginine in the diet. The inclusion of 

 32p^ UQ ethanol-amine or ^^C serine in the food is followed by 

 greater radioactivity in SEP than in lombricine. This also 

 suggests that SEP is indeed the precursor of lombricine and that 

 SEP combines with the amidine group from arginine, as a result of 

 a transamidinase reaction, to give rise to lombricine (Rossitter, 

 et aL, 1960). 



The probable pathways by which lombricine is formed as 

 indicated above is shown in Fig. 35. If this scheme is correct 

 ornithine is produced as a by-product. This substance has not 

 yet been shown to occur in the tissues other than the chloragogen 

 cells where it is probably an intermediate product in the excretory 

 cycle (van Gansen, 1958). In the muscles it is probably present 

 only in trace amounts, and removed by detoxication mechanisms 

 very swiftly thus being rendered unamenable to analysis. 



The associated phosphagen, lombricine phosphate, is formed 

 when high energy phosphate bonds are accepted from ATP. 

 Transphosphorylation from ATP to lombricine is achieved with 

 acetone powders or dialysed enzyme preparations and the maximal 

 enzyme activity is only obtained when Mg ions are present as a 

 co-factor in solution. Activity is gradually lost in dialysed prepara- 

 tions, possibly because of the loss of labile co-factors normally 



