Polyphosphoribosyl

Polyphosphoribosyl is a term used in biochemistry to describe a class of compounds that are derived from ribose-5-phosphate. These compounds are characterized by the presence of multiple phosphate groups attached to a ribose backbone. The most well-known polyphosphoribosyl compounds are the polyphosphoribosyl pyrophosphates (PRPP), which are intermediates in the biosynthesis of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). PRPP is a key molecule in the de novo synthesis of NAD and NADP, which are essential coenzymes in cellular metabolism.

The biosynthesis of PRPP involves the sequential addition of phosphate groups to ribose-5-phosphate, catalyzed by the enzyme phosphoribosyl pyrophosphate synthetase. This process requires the input of energy in the form of ATP and is tightly regulated to ensure the proper levels of NAD and NADP in the cell.

Polyphosphoribosyl compounds also play roles in other biosynthetic pathways. For example, polyphosphoribosyl diphosphate (PRDPP) is an intermediate in the synthesis of purines and pyrimidines, the building blocks of nucleic acids. The polyphosphoribosyl pathway is crucial for maintaining the cellular balance of nucleotides and coenzymes, making it a vital component of cellular metabolism.