NUDT19

Model summary

A soluble human pyrophosphohydrolase that uses a NUDIX catalytic core to hydrolyze pyrophosphate bonds in nucleotide-derived metabolites, with a strong bias toward acyl-coenzyme A and related pools. By sanitizing reactive nucleotide and cofactor species in the cytosol and within the peroxisomal matrix, it supports fatty acid breakdown and protects oxidative metabolism from accumulating toxic intermediates. A C-terminal targeting module likely mediates cytosolic–peroxisomal partitioning, enabling the enzyme to couple nucleotide/cofactor turnover to lipid catabolism and redox homeostasis.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The N-terminus to mid-region is dominated by IPR015797 (NUDIX hydrolase-like domain superfamily, residues 8–288), which frames the overall fold as a metal-dependent pyrophosphohydrolase. Nested within this scaffold is IPR000086 (NUDIX hydrolase domain, residues 11–263), the catalytic core that hydrolyzes diphosphate bonds in nucleoside diphosphate derivatives. The presence of IPR063624 (NUDT19-like, Nudix domain, residues 12–267) refines the chemistry toward the NUDT19 clade, which specializes in oxidized and acylated nucleotide and cofactor substrates. The C-terminal region carries IPR063178 (NUDT19, C-terminal domain, residues 295–355), a module often used for subcellular targeting and substrate-channeling specificity. The full-length assignment to IPR039121 (Acyl-coenzyme A diphosphatase NUDT19 family, residues 8–375) resolves the substrate class: acyl-coenzyme A species and related diphosphate-containing metabolites. This ordered layout—an N-terminal NUDIX catalytic engine followed by a C-terminal targeting/effector domain—causally establishes a soluble, metal-activated pyrophosphohydrolase that acts on CoA and NTP-derived substrates.

2. 02

   From this architecture, the molecular function follows directly.

   The NUDIX catalytic core (IPR000086 within IPR015797/IPR063624) hydrolyzes pyrophosphate bonds in nucleotide diphosphate derivatives, which is the essence of GO:0016462 pyrophosphatase activity. The NUDT19 family signature (IPR039121) biases specificity toward acyl-CoA and oxidized nucleotide pools; the C-terminal domain (IPR063178) likely stabilizes interactions that tune this chemistry in vivo.

3. 03

   This chemistry links to broader pathways.

   Hydrolysis of acyl-CoA and reactive NTP-derived species positions the enzyme within lipid and redox cofactor turnover. In peroxisomes, fatty acid beta-oxidation generates acyl-CoA intermediates and reactive oxygen species; trimming or sanitizing these pools supports GO:0009062 fatty acid catabolic process. By sanitizing oxidized/cofactor pools and modulating acyl-CoA availability, the enzyme indirectly supports peroxisomal oxidative metabolism and prevents accumulation of toxic nucleotide-derived alarmones.

4. 04

   Cellular location is inferred from the soluble NUDIX fold and the presence of a C-terminal targeting module.

   The absence of transmembrane features and the soluble catalytic core argue for a cytosolic enzyme that can be retargeted. The C-terminal domain in NUDT19-like proteins frequently mediates peroxisomal import or matrix retention, aligning with GO:0005829 cytosol and GO:0005782 peroxisomal matrix. Dual residency is mechanistically sensible: cytosolic pools handle nucleotide and acyl-CoA buffering, while peroxisomal pools maintain fatty acid oxidation fidelity.

5. 05

   Mechanistically, the enzyme likely coordinates divalent metal ions at the NUDIX active site to activate water for nucleophilic attack on pyrophosphate bonds, thereby hydrolyzing acyl-CoA and oxidized nucleotide substrates.

   In the cytosol, this activity prevents accumulation of alarmones and limits acyl-CoA-driven lipid signaling; in the peroxisomal matrix, it preserves beta-oxidation efficiency by sanitizing reactive metabolite pools. I hypothesize transient assemblies with peroxisomal import and metabolic machinery—such as PEX5 and PEX14 for matrix delivery, and acyl-CoA-handling enzymes—to channel substrates efficiently and couple nucleotide/cofactor sanitation to fatty acid catabolism.