Xylulose-5-phosphate is an intermediate of the pentose phosphate pathway produced from ribulose-5-phosphate in the reaction catalyzed by phosphopentose epimerase or from glyceraldehyde-3-phosphate and sedoheptulose-7-phosphate in the reaction catalyzed by transketolase.
Xylulose-5-phosphate is also produced in the Calvin cycle by a reversal of the pentose phosphate pathway reaction catalyzed by transketolase.
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2. CO2 Fixation