102 - The Cell 



Table 5-1 (continued) 



General Types; 



Specific N mncs 



Catalytic Action 



Comment 



Aminases 



1. Pyruvic transa- 

 minase 



2. Alanine deamin- 

 ase 



Transfers the amino group 

 ( — NHo) from certain 

 amino acids to pyruvic 

 acid 



CH 3 C COOH 

 II 



O 

 forming alanine 



CH,— C— COO 



I 

 NH, 



Discharges the amino 

 group ( — NHo) from ala- 

 nine, forming pyruvic acid 

 plus ammonia (NH 3 ) and 

 hydrogen peroxide (H-.0 2 ) 



1. Important in reference to 

 the in tercon version of 

 amino acids (p. 156) 



Achieves deamination, an 

 important process in pro- 

 tein catabolism (p. 156); 

 accounts for presence of 

 catalase in most cells 



Digestive Enzymes 

 (all hydrolases) 

 Proteases 

 1 . Pepsin 



2. Trypsin 



3. Chymotrypsin 



4. Carboxypeptidase 



1. An endopeptidase; breaks 

 (hydrolysis) the peptide 

 chain of a protein mole- 

 cule at certain specific 

 points, forming long-chain 

 peptides 



2. An endopeptidase; breaks 

 certain internally placed 

 peptide bonds of long- 

 chain peptides, forming 

 short-chain peptides 



3. Also an endopeptidase; 

 preferentially ruptures 

 bonds bordering upon cer- 

 tain amino acids, namely 

 tyrosine, phenylalanine, 

 and tryptophan 



4. An exopeptidase; splits off 

 terminal amino acids in 

 which the carboxyl 



( — COOH) group is "ex- 

 posed" 



1. Present in the gastric puce 

 of man and other animals; 

 initiates the digestion (p. 

 1 29) of protein components 

 ol lood; requires an acid 

 medium for maximum ac- 

 tivity 



2. Present in pancreatic 

 juices generally; verv effec- 

 tive in the "middle range" 

 ol protein digestion; re- 

 quires alkaline medium 



3. Another pancreatic hy- 

 drolase; cooperates with 

 trypsin in the intermediate 

 range of protein digestion; 

 requires alkaline medium 



4. Present in pancreatic juice; 

 accounts for appearance 

 of single amino acids dur- 

 ing pancreatic digestion; 

 requires alkaline medium 



