HYDROLYZING ENZYMES 



47 



CHO 



H C OH 



HO C H 



CHO 

 H C OH 



H C OH 



I 

 H C OH 



HO C H 



CH 2 OH 



Z-Talose 



CHO 



HO C H 

 HO C H 

 HO C H 

 H C OH 



JH 2 OH 

 d-Talose 



CHO 



HO C H 



I 

 HO C H 



HO C H 



I 

 HO C H 



CH 2 OH 



CHO 



H C OH 



H C OH 



H C OH 



H C OH 



CH,OH 



HO C H 



HO C H 

 HO C H 



;H,OH 



These four unknown 



CHO 



HO C H 

 H C OH 



-OH 

 -OH 



CH 2 OH 



Though many of the above sugars have been synthesized artificially, 

 only three are known to occur naturally, i.e d-glucose (dextrose or grape- 

 sugar), d- man nose and c-galactose. 



Since compounds containing asymmetric carbon atoms are optically 

 active, i.e. can rotate a plane of polarized light, it follows that the sugars 

 under discussion are optically active. 



d-glucose is dextro-rotatory. 



When either d- or Z-glucose is first dissolved in water, it is chemically 

 less active than would be expected of the aldehyde form depicted above. 

 This is explained by assuming that glucose, when first dissolved in water, 

 exists in the condition of a 7-lactone : 



CH 2 OH 



