240 PLANT BIOCHEMISTRY 



COOH 



i 



CHo aspartase HOOCCH 

 I -< ' II +NH3 



CH • NH:!+ HCCOOH 



I 

 COO- 



aspartic arid fiiniaric acid 



The ammonia produced can react with organic acids to form amides. 

 When ammonia reacts with a molecule of glutamic acid in the 

 presence of ATP, Mg+ + , and glutamine synthetase, glutamine is 

 formed. 



HOOCCHoCH,CHCOO- + ATP + NH^ < — ^'"*''"""' > 



I synthetase, Mg"*" * 



NHo+ 



glutamic acid 



H2NOCGH.CH2CHCOO- + ADP + HP04= 



1 



NH3+ 



glutamine 



Asparagine and glutamine are excellent carriers of nitrogen for 

 protein synthesis. These compounds can be broken down to give 

 products available for the synthesis of the particular amino acids and 

 proteins required for growth of an embryo. 



Amino acid oxidases produce ammonia, hydrogen peroxide, and 

 keto acids from amino acids. Keto acids also residt when amino acids 

 lose their amino groups by transamination. The keto acids can be 

 decarboxylaletl, forming the corresponding aldehydes, or they may be 

 utilized through the pathway of the Krebs cycle transformations. 



Fat Metabolism 



The fats and oils of mature seeds are found in relatively large 

 globules. During the resting period and dining germination these 

 globules are reduced in size, thus providing more surface for the 

 action of fat-splitting enzymes. 



In the presence of sufficient water, the lipases of seeds rapidly 

 hydrolyzc the fats and oils to glycerol and fatty acids. Neither the 

 fatty acids nor the glycerol accunudate in large concentrations during 

 germination but are quickly changed to other compounds. The prin- 

 cipal products formed from fats during the germination have been 

 shown to be carbohydrates. 



A suggested mechanism for the conversion of fats into carbohydrates 

 is as follows: (1) Fats and oils are hydrolyzed by lipases to fatty acids 



