STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 155 



of the former reactivity for this enzyme thereby poses the possibihty of its 



role in syntheses and rearrangements of polynucleotide chains. 



Two types of phosphate transfer are recognized at present. In examining 



the formula 







II 

 — C— 0— P— OH 



I 

 OH 



it can be seen that two bonds may be severed, that between and P to 



liberate the phosphoryl moiety 







II 

 — P— OH 



I 

 OH 



and that between ^C and to liberate the phosphate group 







II 

 — 0— P— OH 



I 

 OH 



The use of 0^^-labeled compounds in the cleavage of the bond and the 

 detection of the isotope in the product have permitted the analysis of the 

 reaction type. Most phosphatases have been shown to effect phosphoryl 

 transfer. On the other hand, muscle phosphorylase and sucrose phosphorylase 

 are examples of cleavage at the C — bond. 



2. Kinases 



With compounds such as creatine phosphate, in which the moieties are 

 hnked through an N-P linkage, obviously only phosphoryl transfer is possible. 

 Thus, the kinase, creatine transphosphorylase, affects phosphoryl transfer in 

 the reaction, as shown in formula (XII). 



CH2COOH CH.COOH 



I I 



CHj-N CH,N 



I _ I /> f 



C=NH + ^ ^ r^ ""^"^ C=NH + A-R-0-P-O-P-OH 



I / / ! / I II 



NH2 A-R-O-P-O-P-OrP-OH HN— PO.H, °^ ^^ 



I I ! 1 ' ' 

 OH OH ' OH 



Creatine ATP Creatine phosphate ADP 



(XII) 



Indeed, all kinases tested by the 0^^ method appear to catalyze this type of 

 phosphoryl cleavage, as in the hexokinase reaction shown in formula (XIII). 



