Xyluloosi5fosfaattis

Xyluloosi-5-fosfaatti is an intermediate compound in the pentose phosphate pathway, a metabolic pathway that converts glucose-6-phosphate into a variety of downstream products, including ribose-5-phosphate, which is essential for nucleotide and nucleic acid synthesis. It is also involved in the production of NADPH, a reducing agent used in biosynthesis and to protect against oxidative stress. The compound is a phosphorylated form of xylulose, a five-carbon sugar.

In the oxidative phase of the pentose phosphate pathway, glucose-6-phosphate is converted to ribulose-5-phosphate. This molecule can then be isomerized to ribose-5-phosphate or epimerized to xylulose-5-phosphate. Xylulose-5-phosphate plays a crucial role in the non-oxidative phase of the pathway, where it can be converted into glyceraldehyde-3-phosphate and fructose-6-phosphate through a series of transketolase and transaldolase reactions. These products can then re-enter glycolysis or be used for gluconeogenesis.

The interconversion of ribose-5-phosphate and xylulose-5-phosphate is catalyzed by the enzyme ribose-5-phosphate epimerase. This reversible reaction ensures that the cell can flexibly produce the necessary precursors for nucleotide synthesis or for other metabolic pathways depending on its needs. The pentose phosphate pathway, and therefore xylulose-5-phosphate, is particularly active in tissues with high rates of biosynthesis, such as the liver, adipose tissue, and red blood cells.