Pentose Phosphate Pathway - Outcome

Outcome

The primary results of the Pathway are:

• The generation of reducing equivalents, in the form of NADPH, used in reductive biosynthesis reactions within cells. (e.g. fatty acid synthesis)
• Production of ribose-5-phosphate (R5P), used in the synthesis of nucleotides and nucleic acids.
• Production of erythrose-4-phosphate (E4P), used in the synthesis of aromatic amino acids.

Aromatic amino acids, in turn, are precursors for many biosynthetic pathways, notably including the lignin in wood.

Dietary pentose sugars derived from the digestion of nucleic acids may be metabolized through the pentose phosphate pathway, and the carbon skeletons of dietary carbohydrates may be converted into glycolytic/gluconeogenic intermediates.

In mammals, the PPP occurs exclusively in the cytoplasm, and is found to be most active in the liver, mammary gland and adrenal cortex in the human. The PPP is one of the three main ways the body creates molecules with reducing power, accounting for approximately 60% of NADPH production in humans.

One of the uses of NADPH in the cell is to prevent oxidative stress. It reduces glutathione via glutathione reductase, which converts reactive H₂O₂ into H₂O by glutathione peroxidase. If absent, the H₂O₂ would be converted to hydroxyl free radicals by Fenton chemistry, which can attack the cell. Erythrocytes, for example, generate a large amount of NADPH through the pentose phosphate pathway to use in the reduction of glutathione.

Hydrogen peroxide is also generated for phagocytes in a process often referred to as a respiratory burst.