dndP

dNDP stands for deoxynucleotide diphosphate, a deoxyribonucleotide bearing two phosphate groups. The four canonical forms are dADP, dCDP, dGDP, and dTDP, corresponding to the four bases adenine, cytosine, guanine, and thymine. dNDPs are intermediates in nucleotide metabolism and serve as precursors to the corresponding dNTPs used in DNA synthesis and repair.

In cellular metabolism, dNDPs are interconverted with dNTPs by nucleoside diphosphate kinases (NDPKs). A common reaction is dNDP + ATP → dNTP + ADP, which helps maintain the proper balance of deoxynucleotide triphosphates required for faithful DNA replication. dNDPs can also arise from the hydrolysis of dNTPs or from salvage pathways that phosphorylate deoxynucleosides through sequential kinase steps (dNMP → dNDP → dNTP), using ATP or other phosphate donors.

Enzymology and regulation: NDP kinases are widely conserved enzymes that regulate the interconversion among NDPs and NTPs, contributing to the overall deoxynucleotide pool. The dNTP pool is tightly controlled because imbalances can increase mutation rates during DNA synthesis. Consequently, cellular levels of dNDPs are ordinarily kept low relative to dNTPs, and their measured amounts can inform studies of cell cycle status, DNA damage responses, and cancer biology.

Context and distinction: The term dNDP is used in biochemistry and molecular biology to denote these diphosphates, which differ from dNTPs (triphosphates) and from ribonucleotide diphosphates (which contain ribose). dNDPs play a foundational role in maintaining DNA synthesis fidelity and nucleotide metabolism.