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, 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. In humans, it is found to be most active in the liver, mammary glands, and adrenal cortex. 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. ==Phases==