LUIS F. LELOIR 



However, it has been asserted that aldolase will also split d- 

 tagatose-1 -phosphate (the ketose corresponding to galactose), 

 in which the 3 and 4 OH groups are cis. If such is the case, it is 

 likely that in the synthetic reactions some of the cis compounds 

 are formed but have not been detected owing to their small 

 amounts. 



The action of aldolase on fructose- 1 -phosphate has been 

 given more attention, since the latter was found to be the product 

 of fructose phosphorylation in liver. The utilization of fructose 

 is considered to occur as follows: 



dihydroxyacetone 

 phosphate 



Fructose 



ATP ADP 

 V y ^ fructose- 1- 

 phosphate 



3-phospho- 

 glyceraldehyde 



-*• etc. 



(9) 



ADP 



ATP 



D-glyceraldehyde 



Another enzyme which can transfer three-carbon units is 

 transaldolase (9). It differs from aldolase in that it is the non- 

 phosphorylated dihydroxyacetone residue which is transferred. 

 The following reaction has been used for its detection : 



GHoOH 



I 

 CO 



HOCH 



I 

 HCOH + 



I 

 HCOH 



I 

 HCOH 



CHO 

 HCOH 

 CH2OPO3- 



CH2OPO3-- 



(XVH) 

 Sedoheptulose-7-phosphate 



(xvni) 



Glyceraldehyde-3-phosphate 



(10) 



596 



