722 



NITROGEN METABOLISM AND GROWTH 



15 Protein-amino acids 



Total nitrogen of 17 amino. 



acids 



UJ 



CD. 



; w 



UJ 



ljcb^>, K I V 

 3ru^ SUJCD I UJ _l 



1 2345 5 7 8 9 



I ' ':' 'I ' ' i ' , ' 

 10 20 



10 11 12 



Suj 



i/) CL 



SO 



^2 ^t- Sg 



>-< ^'U 2 . 



-luj -^ to < -• 



Jo. ^UJ ?.-] 



UJ< a Q. < 5 



13 14 15 



16 17 18 stage 



30 



40 50 

 Hours after 



60 70 

 fertilization 



Fig. 2. Percentage changes of 15 protein-contained amino acids and of total nitrogen of 

 1 7 amino acids in early development of Strongylocentrotus purpuratus. Decline of amino acid 

 content of both categories may be related to ammonia production during this period of 

 development resulting from protein catabolism as an energy source. (From Kavanau, 1953.) 



Kavanau (1954b) describes 3 waves of protein synthesis: (j) at midblastula, 

 (2) at completion of hatching and (j) at midgastrulation. There are four periods 

 of yolk protein breakdown: (j) at early cleavage, (2) at late blastula, (j) just 

 before gastrulation and {4) late prism and early pluteus (see Fig. 3). Correlation 

 between to the two processes is high. Kavanau further seeks to show a relationship 

 between respiratory increase and the periods of augmentation of embryonic 

 protein on the one hand, and yolk degradation on the other. He says that 

 "oxidative degradation probably plays a major role in this net loss of amino acids 

 to stage 3". With regard to transformation of yolk protein to embryonic protein 

 Kavanau (1954a) concludes that there is probably very little transfer of large 

 intact polypeptide units from yolk to new protein, for many of the amino acids 

 are found in only relatively small amounts in the peptide fraction. Banhidi and 

 Kavanau (1956) find a correlation between pantothenate content (hence, 

 probably coenzyme A) and protein synthesis in Paracentrotus lividus. They find 

 extraordinary concentrations of free niacin as well (Kavanau and Benhidi, 1956) 

 but establish no certain relationship between them and the synthesis of proteins. 



Possible pertinence to embryonic development of the protein degradation and 



