may play an important role in ammonia detoxification and transmethylation 

 reactions (Kikkila 1951 and Suyama and Tokuhiro 195U b). 



Both non-protein arginine and creatine may serve as phosphate accept- 

 ors; these amino acids are found in muscle tissue mainly in the form of 

 phosphate esters (phosphagens). Just as arginine phosphate appears to be 

 limited to invertebrates, only a trace of creatine being found in Crustacea 

 and other shellfish (Kutscher and Ackermann 1933 )» creatine phosphate is 

 limited to the vertebrates. In loach muscle and eggs, creatine was the 

 major nitrogenous compound extracted (Marushima 19iiil)» 



The synthesis of creatine in mammals is believed to be associated 

 with arginine from which an amidine group is furnished. This association 

 is shown by the work of Bloch and Schoenheimer (19ljl), who fed rats argi- 

 nine labelled isotopically in the amidine nitrogen and found a high con- 

 centration of labelled nitrogen in the amidine group of creatine. whether 

 or not this amidine transfer occurs in fish is not known. 



Other guanidine compounds found in fish muscle— such as octopine, 

 methyl guanidine, arcaine, agmatine, and glycocyamine (Kutscher and Acker- 

 mann 1933 and Kakimoto 195U) — are of unknown significance. Bacterial action 

 may be responsible for the presence of some of these products measured in 

 fish tissue. Agmatine, for example, can be formed by an arginine decarbo- 

 xylase of bacterial origin (Baldwin 1952), 



Two widely distributed imidazole bases in vertebrates, anserine and 

 carnosine, have been found in the muscle tissue of numerous fish (Reay et 

 al. 19U3, Marushima 19hh, and Shewan 1951). Xudaev (1950), however, found 

 neither carnosine nor anserine in fresh-water species, although histidine 

 was present in considerable amounts. Since the fish containing histidine 

 had no -alanine, histidine did not arise from carnosine or anserine In 

 this case* 



Jones (195U and 1955) has reported an enzyme, anserinase, occurring 

 in codling muscle, that is capable of splitting anserine into ^-alanine 

 and 1-methylhistidine, Analyses of extracts of codling muscle showed 

 that before spoilage had occurred, 1-methylhistidine and /3 -alanine in- 

 creased. The same results were obtained with sterile homogenates and cell- 

 free aqueous muscle extracts with added anserine. Later, a partially 

 purified anserinase was obtained by dialysis and acetone fractionation of 

 cell-free muscle extracts; it underwent complete heat inactivation and 

 apparently was Zn^r activated. 



Various betaines have been found in fish muscle; however, little 

 is known of their formation or function (Shewan 1951). It is possible 

 that they take part in biological methylations. Since betaines are wide- 

 spread among plants,- many of them may originate directly from the food 

 supply of an animal, 



Ackermann (1955) has identified by mean3 of paper chromatography 

 various nitrogenous compounds such as taurocyamine, homarine, choline, 

 large amounts of lysine, and other amino acids in the marine snail, 



27 



