What is the meaning of parentheses in "NAD(P)H"?

Question

If someone writes "NAD(P)H is oxidized by ...", does that mean they are referring to both NADH and NADPH?

If so doesn't that lead to confusion when thinking quantitatively since the reactions may proceed at different rates, NAD may be present in a different concentration than NADPH, etc?

If not, what do the parentheses around P mean?

Answer 1

If an enzyme is called $\mathrm{NAD(P)H}$-dependent, that means it is using both $\mathrm{NAD^+/NADH}$ and $\mathrm{NADP^+/NADPH}$ as its cofactors. For example, most oxidoreductases are $\mathrm{NAD(P)H}$-dependent, which are able to oxidize a relevant substrate by transferring a hydride ($\ce{H−}$) group to a nicotinamide adenine dinucleotide cofactor (either $\mathrm{NAD^+}$ or $\mathrm{NADP^+}$), resulting in their reduced forms, $\mathrm{NADH}$ or $\mathrm{NADPH}$ (Ref.1):

You can find a list of $\mathrm{NAD(P)H}$-dependent oxidoreductases within Reference 1.

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Reference:

1. Lara Sellés Vidal, Ciarán L. Kelly, Paweł M. Mordaka, John T. Heap, "Review of NAD(P)H-dependent oxidoreductases: Properties, engineering and application," Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics 2018, 1866(2), 327-347 (https://doi.org/10.1016/j.bbapap.2017.11.005).