NT5C3B Human

5’-Nucleotidase, Cytosolic IIIB (NT5C3B) is an enzyme that plays a crucial role in cellular metabolism by catalyzing the hydrolytic dephosphorylation of nucleoside monophosphates to their corresponding nucleosides and phosphate. This enzyme is part of the broader family of 5’-nucleotidases, which are distributed across various cellular locations and are involved in numerous physiological processes.

5’-Nucleotidases, including NT5C3B, are responsible for the dephosphorylation of 5’-ribonucleotides and 5’-deoxyribonucleotides. The general reaction catalyzed by these enzymes can be represented as follows:

$$\text{5'-nucleotide} + \text{H}_2\text{O} \rightarrow \text{nucleoside} + \text{phosphate}$$

This reaction is essential for the regulation of nucleotide pools within the cell, impacting processes such as nucleic acid repair, signal transduction, and cell-to-cell communication .

The structure of 5’-nucleotidases typically includes a substrate-binding pocket within the C-terminal domain. The aromatic purine motif of the substrate is often stacked between phenylalanine residues, facilitating the catalytic mechanism. The enzyme’s active site involves a nucleophilic attack by a hydroxyl moiety coordinated by zinc on the substrate phosphorus, with the nucleoside acting as a leaving group .

In mammalian cells, 5’-nucleotidases exist in both membrane-bound and soluble forms. NT5C3B is one of the cytosolic isoforms, which can be differentiated based on their substrate affinities. These enzymes are involved in the purine salvage pathway, contributing to the synthesis of nucleotides and maintaining cellular nucleotide balance .

NT5C3B and other 5’-nucleotidases play multifaceted roles in cellular metabolism. They are involved in:

• Purine and Pyrimidine Salvage Pathways: Recycling nucleotides for nucleic acid synthesis.
• Nucleic Acid Repair: Ensuring the integrity of genetic material.
• Signal Transduction: Modulating cellular responses to external signals.
• Cell-to-Cell Communication: Facilitating interactions between cells.
• Control of Nucleotide Pools: Regulating the levels of ribo- and deoxyribonucleotides .

Misregulation of nucleotide metabolism and deficiencies in nucleotidase activity are associated with various diseases. Understanding the function and regulation of NT5C3B can provide insights into potential therapeutic targets for conditions related to nucleotide imbalance .