---
pmid: '20722631'
title: HDHD1, which is often deleted in X-linked ichthyosis, encodes a pseudouridine-5'-phosphatase.
authors:
- Preumont A
- Rzem R
- Vertommen D
- Van Schaftingen E
journal: Biochem J
year: '2010'
full_text_available: false
doi: 10.1042/BJ20100174
pubmed_publication_types:
- Journal Article
- Research Support, Non-U.S. Gov't
publication_type: PRIMARY_RESEARCH
---

# HDHD1, which is often deleted in X-linked ichthyosis, encodes a pseudouridine-5'-phosphatase.
**Authors:** Preumont A, Rzem R, Vertommen D, Van Schaftingen E
**Journal:** Biochem J (2010)
**DOI:** [10.1042/BJ20100174](https://doi.org/10.1042/BJ20100174)

## Abstract

1. Biochem J. 2010 Oct 15;431(2):237-44. doi: 10.1042/BJ20100174.

HDHD1, which is often deleted in X-linked ichthyosis, encodes a
pseudouridine-5'-phosphatase.

Preumont A(1), Rzem R, Vertommen D, Van Schaftingen E.

Author information:
(1)de Duve Institute, Université Catholique de Louvain, Brussels, Belgium.

Pseudouridine, the fifth-most abundant nucleoside in RNA, is not metabolized in
mammals, but is excreted intact in urine. The purpose of the present work was to
search for an enzyme that would dephosphorylate pseudouridine 5'-phosphate, a
potential intermediate in RNA degradation. We show that human erythrocytes
contain a pseudouridine-5'-phosphatase displaying a Km ≤ 1 μM for its substrate.
The activity of the partially purified enzyme was dependent on Mg2+, and was
inhibited by Ca2+ and vanadate, suggesting that it belonged to the 'haloacid
dehalogenase' family of phosphatases. Its low molecular mass (26 kDa) suggested
that this phosphatase could correspond to the protein encoded by the HDHD1
(haloacid dehalogenase-like hydrolase domain-containing 1) gene, present next to
the STS (steroid sulfatase) gene on human chromosome Xp22. Purified human
recombinant HDHD1 dephosphorylated pseudouridine 5'-phosphate with a kcat of 1.6
s-1, a Km of 0.3 μM and a catalytic efficiency at least 1000-fold higher than
that on which it acted on other phosphate esters, including 5'-UMP. The
molecular identity of pseudouridine-5'-phosphatase was confirmed by the finding
that its activity was negligible (<10% of controls) in extracts of B-cell
lymphoblasts or erythrocytes from X-linked ichthyosis patients harbouring a
combined deletion of the STS gene (the X-linked ichthyosis gene) and the HDHD1
gene. Furthermore, pseudouridine-5'-phosphatase activity was 1.5-fold higher in
erythrocytes from women compared with men, in agreement with the HDHD1 gene
undergoing only partial inactivation in females. In conclusion, HDHD1 is a
phosphatase specifically involved in dephosphorylation of a modified nucleotide
present in RNA.

DOI: 10.1042/BJ20100174
PMID: 20722631 [Indexed for MEDLINE]