Nicotinamide adenine dinucleotide phosphate

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Nicotinamide adenine dinucleotide phosphate (NADP+) is a coenzyme that plays a crucial role in various biochemical processes. It is a derivative of nicotinamide adenine dinucleotide (NAD+) and is involved in anabolic reactions, such as lipid and nucleic acid synthesis, where it acts as a reducing agent.

Structure

NADP+ consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base, and the other contains nicotinamide. The additional phosphate group distinguishes NADP+ from NAD+.

Function

NADP+ is primarily involved in anabolic reactions, which are processes that build larger molecules from smaller ones. It serves as a cofactor in oxidation-reduction reactions, where it alternates between its oxidized form (NADP+) and its reduced form (NADPH). NADPH provides the reducing power needed for various biosynthetic reactions, including the synthesis of fatty acids and cholesterol.

Role in Photosynthesis

In photosynthesis, NADP+ is reduced to NADPH in the light-dependent reactions. NADPH then provides the reducing power for the Calvin cycle, which synthesizes glucose from carbon dioxide and water.

Role in Cellular Respiration

While NADP+ is less involved in cellular respiration compared to NAD+, it still plays a role in the pentose phosphate pathway, which generates NADPH and ribose-5-phosphate for nucleotide synthesis.

Biosynthesis

NADP+ is synthesized from NAD+ by the enzyme NAD+ kinase, which transfers a phosphate group from ATP to NAD+.

Clinical Significance

Abnormal levels of NADP+ and NADPH can be associated with various metabolic disorders and diseases. For example, a deficiency in NADPH can lead to impaired immune function and increased susceptibility to oxidative stress.

See also

• Nicotinamide adenine dinucleotide
• Photosynthesis
• Cellular respiration
• Pentose phosphate pathway
• Anabolic reactions