The non-oxidative phase  generates  ribose precursors

The non-oxidative phase of  the pathway,  including the following reactions, converts pentose-5-phosphate to other sugars.

i)  Ribulose-5-phosphate  is acted on by ribulose-5-phosphate epimerase, which  changes the configuration at carbon  3  fonning  xylulose-5- phosphate, and  also by  the enzyme ribose-5-phosphate ketoisomerase,  which converts ribulose-5-phosphate to ribose-5-phosphate.

ii)  The next  step involves the action of  the enzyme  transketolase.  Transketolase with the help of TDP and Mg++  transfers carbons land 2 of xylulose-5-phosphate to ribose-5-phosphate forming sedoheptulose-7-phosphate  and glyceraldehyde-3-phosphate