HMP Shunt (Pentose Phosphate Pathway)

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The HMP Shunt, also known as the Pentose Phosphate Pathway or the Phosphogluconate Pathway, is a biochemical pathway that serves as an alternative metabolic pathway for glucose.

The first phase is oxidative and irreversible. Glucose-6-phosphate (G6P) is converted via series of steps into Ribulose-5-phosphate. The most important catalytic enzyme is Glucose-6-phosphate Dehydrogenase (G6PD), which produces NADPH in the process. This is the major source of NADPH in the cell, and decreased NADPH can be seen in G6PD Deficiency.

The second phase is non-oxidative and reversible, and involves transketolase as a major enzyme. Ribulose-5-phosphate is converted into Ribose-5-phosphate, which can undergo further reactions to produce Fructose-6-phosphate and Glyceraldehyde-3-phosphate. Ribose-5-phosphate is an important precursor to PRPP in the Purine and Pyrimidine Synthesis pathways. Of note, the action of transketolase requires Vitamin B1/Thiamine as a cofactor.

Find this HMP Shunt mnemonic and more mnemonics for Biochemical Pathways among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.