Introduction

BIOCHEMISTRY 3(2+1)
Lesson 21 : Pentose Phosphate Pathway or HMP Shunt

Introduction

The pentose phosphate pathway (also called phosphogluconate pathway, or hexose monophosphate shunt [HMP shunt]) is a process that generates NADPH and pentoses (5-carbon) sugars. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars. This pathway is an alternative to glycolysis. While it does involve oxidation of glucose, its primary role is anabolic rather than catabolic.

It is a metabolic pathway, alternative to that of glycolysis, of carbohydrate interconversion: hexose-6-phosphate is converted into pentose-phosphate and carbon dioxide. The principal functions of the pathway are the production of deoxyribose and ribose sugars for nucleic-acid synthesis; the generation of reducing power in the form of NADPH for fatty-acid and/or steroid synthesis; and the interconversion of carbohydrates. In animals, the pathway occurs mainly in tissues that synthesize steroids and fatty acids (e.g. liver, mammary glands, and adrenal gland).

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