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Nicotinate phosphoribosyltransferase (NAPRTase), subgroup A. Nicotinate phosphoribosyltransferase catalyses the formation of NAMN and PPi from 5-phosphoribosy -1-pyrophosphate (PRPP) and nicotinic acid, this is the first, and also rate limiting, reaction in the NAD salvage synthesis. This salvage pathway serves to recycle NAD degradation products. This subgroup is present in bacteria and eukaryota (except funghi).