Detection and characterisation of NAD(P)H-diaphorase activity in Dictyostelium discoideum cells (Protozoa)

In Dictyostelium discoideum (D. dis-coideum), compounds generating nitric oxide (NO) inhibit its aggregation and differentia-tion without altering cyclic guanosine monophosphate (cGMP) production. They do it by preventing initiation of cyclic adenosine monophosphate (cAMP) pulses. Furthermore, these compounds stimulate adenosine dipho-sphate (ADP)-ribosylation of a 41 kDa cytoso-lic protein and regulate the glyceraldehyde-3-phospate dehydrogenase activity. Yet, although D. discoideum cells produce NO at a relatively constant rate at the onset of their developmen-tal cycle, there is still no evidence of the pres-ence of nitric oxide synthase (NOS) enzymes. In this work, we detect the nicotinamide ade-nine dinucleotide phosphate-diaphorase (NADPH-d) activity in D. discoideum and we characterise it by specific inhibitors and phys-ical-chemical conditions that allegedly distin-guish between NOS-related and-unrelated NADPH-d activity. © A. Amaroli and M.G. Chessa, 2012.