34 



W. G. OVEREND AND M. STAGEY 



TABLE IV 

 Rates of Acidic Hydrolysis of Some Pentose Phosphates 



Compound 



Normality of acid Temp., °C. K X 10'° 



Ribose-1 -phosphate 

 Ribose-3-phosphate 



Ribose-5-phosphate 



Xylose-1 -phosphate 

 Xylose -5-phosphate 



0.50 

 0.01 

 0.25 

 0.01 

 0.25 

 0.10 

 1.00 



25 

 100 

 100 

 100 

 100 



36 

 100 



1200 

 -1.7 

 -4.5 

 -0.3 

 -0.5 

 6.21 

 3-4 



Reference 



174 

 175 

 176 



175 

 176 

 177 

 178 



1 a 1 



"Constants are calculated from the formula K = - logio or more usually K = logi 



t a — X h — ti 



, when a is the initial concentration of the substance and the time (t) is expressed in minutes. 



TABLE V 

 Specific Rotations of some Pentose Phosphate Esters 



phosphates are usually more acid-labile than the a-forms. Levene and 

 Stiller'^* demonstrated that a pentose-3-phosphate hydrolyzes much more 

 rapidly in acid solution than does the 5-isomer. For example, ribose-3- 

 phosphate hydrolyzes 5 to 9 times faster than ribose-5-phosphate under 

 identical conditions. This method of distinguishing between the 3- and 5- 

 phosphate esters of ribose is applicable not only to the compounds them- 



175 p. A. Levene and E. T. Stiller, /. Biol. Chem. 104, 299 (1934). 

 "8 H. G. Albaum and W. W. Umbreit, /. Biol. Chem. 167, 369 (1947). 

 1" W. R. Meagher and W. Z. Hassid, /. Am. Chem. Soc. 68, 2135 (1946). 

 178 p. A. Levene and A. L. Raymond, /. Biol. Chem. 102, 347 (1933). 

 "9 P. A. Levene and S. A. Harris, J. Biol. Chem. 95, 755 (1932). 



180 A. M. Michelson and A. R. Todd, /. Chem. Soc. 1949, 2476. 



181 P. A. Levene and C. C. Christman, /. Biol. Chem. 123, 607 (1938). 



