i LIVING MATTER 27 



I. Aliphatic or Fatty Series. 



1. Mono-aniino-mono-carboxylic acids : glycine 



alanine 

 valine 

 leucine 

 isoleucine. 



2. Mono-amino-oxy-mono-carboxylic acids : serine. 



3. Mono-amino-tliio-mono-carboxylic acids : cysteine and cystine. 



4. Mono-amino-di-carboxylic acids : aspartic acid 



glutamic acid. 



5. Di-amino-moiio-carboxylic acids : lysine 



arginine. 



6. Di-amino-oxy-mono-carboxylic acids : di-arnino-tri-oxy-dodecanic acid. 



II. Aromatic Series. 



1. Mono-amino-mono-carboxylic acids : phenylalanine. 



2. Mono-amino-oxy-mono-carboxylic acids : tyrosine. 



III. Heterocyclic Compounds. 



1. Mono-amino-mono-carboxylic acids: proliiie (a-pyrrolidine-carboxylic acid) 



tryptophane (indole - a - ammo - pro- 



pionic acid) 

 liistidine (imidazole - a - ammo - pro- 



pionic acid). 



2. Mono-amino-oxy-mono-carboxylic acids : oxy -proliiie (oxy-pyrrolidine- 



carboxylic acid). 



Some chemists further regard the carbohydrate (glucosamine) 

 group as a cleavage product of proteins : this group, however, 

 occupies a special position, inasmuch as it is absent in many 

 proteins, while in others its presence is doubtful, and, moreover, 

 those which contain large amounts of it 'are by many considered 

 to be compound proteins (gluco-proteins). We may suppose that 

 as all proteins contain units which exhibit great affinity to the 

 molecule of a carbohydrate, since they contain six carbon atoms, 

 there is a possible transition from this group to the carbohydrate 

 molecule. Lysine, e.g., which is an amino-acid invariably present 

 among the cleavage products of all proteins, has a formula very 

 like that of glucosamine and glucose, as will be seen from the 

 following table : 



CH 2 (OH) CH 2 (OH) CH 2 (NH 2 ) 



CH(OH) CH(OH) CH 2 



CH(OH) CH(OH) CH 2 



CH(OH) CH(OH) CH, 



( ' 1 



CH(OH) CH(NH 2 ) CH(NH 2 ) 



CH : COOH 



CH: 



Glucose Glucosamine Lysine 



