Biosynthesis of Enzymes and their Origin 



457 



amylase. ATP is absolutely needed, two amino acids (threonine and histidine in 

 case of dog pancreas), ribonucleic acid and a protein fraction which can be re- 

 placed by a purified enzyme preparation, which catalyses the acyl activation of 

 threonine and histidine. 



Table i 



Purity and specific activity of amylase isolated from different 

 subcellular fractions of pigeon pancreas 



Slices were incubated in Krebs' bicarbonate solution in the presence of an amino 

 acid mixture, 0-6% glucose and [i^COOHJglycine and homogenized and fractionated 

 after experiment in isotonic sucrose. 



Summing up we may say that the enzyme amylase is formed through an inter- 

 mediary stage, and the synthetic transformation of the precursor into the active 

 enzyme is bound to the presence of ribonucleic acid (RNA). If the existence of 

 precursor proteins may be found in the course of the formation of other enzymes 

 also, it is conceivable that one and the same precursor might serve for the pro- 

 duction of different specific proteins. The chemistry of corticotropin and the 

 melanophore-stimulating hormone has revealed that the same unit consisting of 

 13 amino acids occurs in both of them. 



