Do metabolic HAD phosphatases moonlight as protein phosphatases?

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Mammalian haloacid dehalogenase (HAD)-type phosphatases dephosphorylate diverse substrates, including small metabolites and phosphorylated proteins.
• Capped HAD phosphatases utilize cap domains to regulate active site access and determine substrate specificity.
• While some capped HAD phosphatases affect protein phosphorylation, structural data often suggest small metabolite roles.

Purpose of the Study:

• To review the structures, functions, and disease implications of three related capped HAD phosphatases: PDXP, PGP, and LHPP.
• To examine the evidence for both small metabolite and protein phosphatase activities of these enzymes.
• To contextualize these activities within the broader scope of their biological functions.

Main Methods:

• Literature review of structural, functional, and disease-related studies.
• Analysis of existing data on substrate specificity and enzyme mechanisms.
• Synthesis of information regarding pyridoxal phosphatase (PDXP), phosphoglycerate phosphatase (PGP), and phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP).

Main Results:

• The review details the structural features and known functions of PDXP, PGP, and LHPP.
• Evidence supporting both small metabolite and protein dephosphorylation activities is presented for these enzymes.
• The diverse biological roles stemming from their phosphatase activities are discussed.

Conclusions:

• PDXP, PGP, and LHPP are closely related capped HAD phosphatases with significant roles in cellular metabolism and signaling.
• Understanding their dual substrate specificity (small molecules and proteins) is crucial for elucidating their functions.
• Further research into these phosphatases may reveal novel therapeutic targets for associated diseases.