Non-specific acid phosphatases (class A)

 

Non-specific acid phosphatases (NSAPs) are bacterial enzymes that catalyse the dephosphorylation of orthophosphoric monoesters to alcohol and phosphate, in addition to being able to catalyse transphosphorylation. They show broad specificity, being able to phosphorylate a wide range of hydroxy compounds, including p-nitrophenyl phosphate, carbamoyl phosphate, pyrophosphate, glucose-6-phosphate, and ATP.

During active catalysis, an activated phospho-enzyme (via the nucleophilic His residue) intermediate is formed that is able to transfer its phosphate group to water, glucose or inosine. Nonspecific acid phosphatases share a conserved active site with mammalian glucose-6-phosphatases (G6Pase).

They may be divided into three classes (A, B, C) based on sequence similarity.The Escherichia blattae enzyme (EB-NSAP) is a class A NSAP.

 

Reference Protein and Structure

Sequence
Q9S1A6 UniProt (3.1.3.2) IPR011158 (Sequence Homologues) (PDB Homologues)
Biological species
Shimwellia blattae (Bacteria) Uniprot
PDB
1d2t - CRYSTAL STRUCTURE OF ACID PHOSPHATASE FROM ESCHERICHIA BLATTAE (1.9 Å) PDBe PDBsum 1d2t
Catalytic CATH Domains
1.20.144.10 CATHdb (see all for 1d2t)
Click To Show Structure

Enzyme Reaction (EC:3.1.3.2)

phosphate monoester dianion
CHEBI:67140ChEBI
+
water
CHEBI:15377ChEBI
→
alcohol
CHEBI:30879ChEBI
+
hydrogenphosphate
CHEBI:43474ChEBI
Alternative enzyme names: Acid monophosphatase, Acid nucleoside diphosphate phosphatase, Acid phosphohydrolase, Acid phosphomonoester hydrolase, Acid phosphomonoesterase, Glycerophosphatase, Orthophosphoric-monoester phosphohydrolase (acid optimum), Phosphomonoesterase, Uteroferrin,

Enzyme Mechanism

Introduction

The reaction proceeds via a phosphoenzyme intermediate. His 189 functions as a nucleophile to attack the phosphate group, while the departing alcohol is protonated by His 150. Asp 193 functions to modify the nucleophilic properties of His 189, while Arg 183 is proposed to help stabilise the resulting phosphohistidine intermediate. In the second step, the phosphohistidine intermediate is hydrolysed by a water molecule that is deprotonated by His 150.

Catalytic Residues Roles

UniProt PDB* (1d2t)
His168 His150A General acid/base. Protonates the departing alcohol on attack by His 189. Deprotonates the water molecule that hydrolyses the phosphoenzyme intermediate. proton shuttle (general acid/base)
Arg201 Arg183A Proposed to stabilise the phosphoenzyme intermediate. electrostatic stabiliser
His207 His189A Catalytic nucleophile. Attacks the phosphate group of the substrate, leading to formation of a covalent phosphoenzyme intermediate. covalent catalysis
Asp211 Asp193A Modifies the nucleophilic properties of His 189. enhance reactivity
*PDB label guide - RESx(y)B(C) - RES: Residue Name; x: Residue ID in PDB file; y: Residue ID in PDB sequence if different from PDB file; B: PDB Chain; C: Biological Assembly Chain if different from PDB. If label is "Not Found" it means this residue is not found in the reference PDB.

Chemical Components

References

  1. Ishikawa K et al. (2000), EMBO J, 19, 2412-2423. X-ray structures of a novel acid phosphatase from Escherichia blattae and its complex with the transition-state analog molybdate. DOI:10.1093/emboj/19.11.2412. PMID:10835340.
  2. Manabe F et al. (2011), Extremophiles, 15, 359-364. Conserved residues in membrane-bound acid pyrophosphatase from Sulfolobus tokodaii, a thermoacidophilic archaeon. DOI:10.1007/s00792-011-0367-2. PMID:21461791.
  3. Makde RD et al. (2007), Biochemistry, 46, 2079-2090. Structure and Mutational Analysis of the PhoN Protein ofSalmonella typhimuriumProvide Insight into Mechanistic Details‡. DOI:10.1021/bi062180g. PMID:17263560.
  4. Tanaka N et al. (2003), Org Biomol Chem, 1, 2833-. Phosphorylation and dephosphorylation of polyhydroxy compounds by class A bacterial acid phosphatases. DOI:10.1039/b304012g.
  5. Neuwald AF (1997), Protein Sci, 6, 1764-1767. An unexpected structural relationship between integral membrane phosphatases and soluble haloperoxidases. DOI:10.1002/pro.5560060817. PMID:9260289.

Step 1.

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Catalytic Residues Roles

Residue Roles
His150A proton shuttle (general acid/base)
Asp193A enhance reactivity
His189A covalent catalysis
Arg183A electrostatic stabiliser

Chemical Components

Step 1.

Contributors

Steven Smith, Gemma L. Holliday