The Effect of Cysteine on the Methionine 



Content of the Animal and Plant 



Organism 



SIMION OERIU 



Dept. of Chemotherapy of the Academy of the Rumanian People's Republic and 



Dept. of Biochemistry of the Medicopharmaceutical Institute, 



Bucharest, Rumania 



In investigations in the field of prophylaxis of the process of ageing and the 

 prolongation of life C. I. Parhon, S. Oeriu & I. Tanase studied the content of 

 sulphur-containing amino acids, in different conditions, in animals (rats) of 

 different ages [12]. 



As sulphydryl groups have an important significance in oxido-reductive pro- 

 cesses, in detoxication of the organism and in metabolic processes in general, 

 we assumed that they also played a biological part in the process of ageing. 



Our investigations showed that the methionine content of the serum of rats 

 decreased with age while the cystine content increased [13].* 



In order to observe the shifts in the oxido-reductive process in the cystine- 

 cysteine system under the influence of methionine and cysteine, we determined 

 the contents of methionine, cystine and cysteine in the serum of rats of different 

 ages before and after the intramuscular administration of methionine or cysteine 

 (50 mg/kg body weight daily for 16-20 days). 



The administration of cysteine or methionine to young or adult rats led to 

 an insignificant change in the methionine content. These findings confirm the 

 results obtained by Arnstein & Crawhall [2] after the administration of cysteine 

 labelled with '^-^S to adult rats, and also the results of Stekol & Weiss [16] after 

 the administration of cystine labelled with ^^S to young rats. 



Old animals behave differently: the administration of cysteine, under the 

 same conditions, leads to a marked increase (60-64'X)) in methionine. It may 

 be supposed that the increase in the methionine in old animals after adminis- 

 tration of cysteine is a very profound biological process, associated with the 

 age of the animal. 



The investigations of du Vigneaud [6] into the transformation of methionine 

 into cysteine in growing rats to which, in the absence of cysteine from their diet, 

 they administered, for 36 days in the food, methionine which, as well as being 



* Methionine was determined by the method of Hess & Sullivan [8], cysteine -I cystine 

 by that of Wassel [19], cysteine and cystine were determined polarographically. For this 

 purpose we used acid hydrolysis of the protein according to the method of Brdicka [3, 4] 

 and Tropp [18]. 



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