158 F. Dickens, G. E. Glock and P. McLean 



(b) Anaerobic pentose phosphate pathway 



The pentose phosphates formed from Ru5P in the oxidative 

 stages are able to undergo a fascinating series of changes 

 which have been fully reviewed recently (Racker, 1957; 



R5P 



(3)J 



GA3P 



SH7P 



'DHA* TctroseP 



F6P 



(3)t 



Ru5P 



(2) 



Xu5P. 



F6P + GA3P 



(I) Isomerase 

 (3)Transketolase 



(2)Epimerase 

 (4)Transaldo!ase 



Fig. 3. Anaerobic pentose phosphate cycle. 

 DHA" indicates the dihydroxy acetone moiety of SH7P which is transferred 

 to GASP by TA. Overall reaction : 2 F6P + 1 triose P ^ 3 Pentose P. 



Horecker and Hiatt, 1958; Dickens, 19586). The following 

 enzymic reactions occur (cf. Fig. 3): 



(1) D-Ru5P^D-R5P (ribose phosphate isomerase) 



(2) D-Ru5P ;f=^ d-Xu5P (ketopentose phosphate epimerase) 



(3) D-Xu5P + D-R5P ^ SH7P + GA3P (TK) 



(4) SH7P + GA3P ^ F6P + D-Er4P (TA) 



(5) D-Er4P + D-Xu5P — F6P + GA3P (TK) 



(6) Overall: 3 Ru5P ^ 2 F6P + GA3P 



