STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 165 



C^^-fructose in a phosphate-free medium. These reactions may be \\Titten as 

 follows: 



glucose-1-P^^ + enzyme (E) ^ P^^ + glycosyl-E ^— glucose-1-P^- + E 



C'*-fructose 

 glucose -l-fructoside + E ^fructose + glucosyl-E ~ - " ^ ghicose-l-C'*-fructoside + E 



Thus, glycosyl-enzyme complexes are considered to be important inter- 

 mediates in the action of this and other transglycosidases. 



2. Transglycosidases and Hydrolases 



Extracts of animal organs contain a branching enzyme, which, acting in 

 conjunction with phosphorylase, produces a branched polysaccharide 

 resembhng glycogen. The branching enzyme removes short terminal chains 

 of 1, 4 linked glucose units and links them to free primary hydro xyls at the 

 Cg of glucose moieties wdthin amylose chains, thereby estabhshing branch 

 points and multiple sites for the further action of phosphorylase, as shown 

 in formula (XXI). 



G — G — (jr — G — G — G — G — G — Gr 



I 

 G — Gr — G— G — G — G — G — G 



I branching enzyme 



G — G — G— — G G — G — G — G — G — G 



I I 



G— G— G— G— G G— 1— P G— G— G— G— G— G— G— G 



G— G— G— G phosphorylase G— G— G— G— G— G 



I I 



G — G — G — G G — G — G — -G — G — G 



(XXI) 



A somewhat similar branching enzyme, Q enzyme, is also known m bacteria 

 (Hassid, 1954). As summarized by Hassid (1954) and Kalckar (1954), a large 

 number of nonphosphorylytic transglycosidases have now been recognized. 

 These include ^raws-O-glycosidases and fraws-A^-glycosidases, in which 

 glycosyl-enzyme complexes are beheved to be the critical intermediates. In 

 -the former group are enzymes which operate on disaccharides and longer 

 polysaccharide chains. Of the enzymes operating on disaccharides may be 

 Usted a number of hydrolases, such as invertase and lactase, which may not 

 only cleave their respective substrates to free monosaccharides but are also 

 capable of transferrmg one component to another mole of acceptor, e.g., 

 invertase will cleave sucrose (1,2 glucosyl fructoside) to glucose and fructose, 

 but is also capable of acting both as a transfructosidase and a transgluco- 

 sidase. Preparations of these enzymes wiU also transfer moieties to amino 



