# Cell Study: A Selenium Enzyme Breaks Down NAD+ in Mitochondria

_Evidence Level: Preliminary · Jia X et al., Cell, DOI 10.1016/j.cell.2026.01.033_

*NAD+ hydrolysis catalyzed by SelO is required for mitochondrial homeostasis.*

- **Evidence Level**: Preliminary
- **Why this grade**: Lab experiments in mammalian cells and bacteria; whether this mechanism matters for human health was not tested.
- **Facts**: Design: Lab study · Funding: National Natural Science Foundation of China; National Major Science and…
- **Population**: Cell or computational study
- **Publication Types**: Journal Article
- **Journal**: Cell
- **Sample Size**: N/A
- **Authors**: Jia X, Zhang T, Yang C, Liu K, Wu L, Diao L, Yang Y, Wu J, Li Y, Sun W, Zhang K, Jiang Y, Zhao Y, Zhang X, Jiang P, Yu Q, Xiang S, Fu Y, Wang T
- **Graded and published**: 2026-03-09
- **Last edited**: 2026-10-19
- **Topics**: Mitochondria, Aging Biology
- **DOI**: https://doi.org/10.1016/j.cell.2026.01.033
- **Original Source**: https://pubmed.ncbi.nlm.nih.gov/41806834/

## Summary

NAD+ is a helper molecule that many of life's processes depend on. How it gets broken down inside mitochondria, the power plants of our cells, was poorly understood. This study found one route: an enzyme called SelO splits NAD+ into two smaller building blocks, one of them NMN.

The researchers found SelO with a computer search for proteins that might bind NAD+. They then tested it in mammalian cells and in bacteria. SelO needs manganese as a helper. Its key part is a building block at the end of the enzyme that contains selenium. SelO attaches directly to the enzymes that burn fat, and through this link it strongly shapes how cells use fat. It switches on when mitochondria run at full speed and their interior becomes less acidic. In this way, the breakdown protects mitochondria from lasting overload.

This is basic research in cells and bacteria. What it means for human health was not studied. Still, it points to a protective job for the controlled breakdown of NAD+ inside mitochondria.

## Practical Takeaway

The enzyme SelO breaks down NAD+ in mitochondria when they run at full speed, protecting them from overload.

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_Canonical: https://longevity-germany.com/en/research/cell-study-a-selenium-enzyme-breaks-down-nad-in-mitochondria · Part of Longevity Cities · Updated 2026-10-19_