Trying to understand Photosynthesis better. I understand the NADP+ is reduced to NADPH in light dependent reactions and NADPH is then recycled back into NADP+ in the Calvin cycle. What I don't understand is where does the NADP+ come from initially?

Specifically I am asking with regards to its presence in the stroma within the chloroplasts of a plant cell. Where do plants get NADP+ from in order to assist in the production of sugar?

  • 1
    $\begingroup$ The simple answer is that plants synthesize it in the same way as they do most other cellular molecules. You can find the details in standard texts. However, I assume that is not what you are after. If so, you need to explain — at present your question is unclear, at least to me. $\endgroup$
    – David
    Aug 21 '18 at 10:51

Niacin (better known as vitamin B3) and nicotinamide are both precursors of the coenzymes NAD and NADP in vivo. As you can see below, the biosynthesis of NADP+ proceeds as follows, when nicotinamide combines with a basic ingredient, a sugar phosphate:

Biosynthesis of NADP+

The sugar phosphate precursor can also form AMP and GMP, also important molecules in the cell, when it reacts with the nucleobases adenine and guanine (A and G from the 'ladder' that bridges the DNA helix).

Just as an additional funfact, some bacteria such as Plasmodium falciparum and Toxoplasma gondii cannot synthesize nicotinamide themselves, because they lack the genes for it. Instead, they salvage the enzymes from eukaryotic hosts. This is an example of an incomplete biochemical toolkit giving rise to parasitism.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.