PROSITE documentation PDOC00136

Acylphosphatase-like domain signatures and profile

Acylphosphatase (EC 3.6.1.7) [1,2] catalyzes the hydrolysis of various acyl phosphate carboxyl-phosphate bonds such as carbamyl phosphate, succinyl phosphate, 1,3-diphosphoglycerate, etc. The physiological role of this enzyme is not yet clear. Acylphosphatase is a small protein of around 100 amino-acid residues. Two different isoenzymes are expressed in mammalian tissues: muscle type (MT) acylphosphatase is prevalently found in the skeletal muscle and heart, whereas the organ common type (CT) acylphosphatase is expressed in erythrocytes, brain and testis.

While acylphosphatase have been so far only characterized in vertebrates, there are a number of bacterial and archebacterial hypothetical proteins that are highly similar to that enzyme and that probably possess the same activity. These proteins are:

• Escherichia coli probable acylphosphatase yccX.
• Bacillus subtilis probable acylphosphatase yflL.
• Archaeoglobus fulgidus probable acylphosphatase AF0818.

An acylphosphatase-like domain is also found in the N-terminus of prokaryotic hydrogenase maturation protein hypF [3,4].

The acylphosphatase-like domain forms a compact, pear-shaped, stucture (see <PDB:2ACY>). It has a globular α/β fold, consisting of a β sheet with five antiparallel strands and two α helices packed parallel on the same side of the sheet, forming an α/β sandwich protein. The acylphosphatase-like domain is stabilized by intramolecular contacts of the two antiparallel amphipatic α-helices, which pack their hydrophobic residues against the inner face of the β-sheet, leaving no core cavities in the proteins structure [4,5].

As signature patterns, we selected two conserved regions. The first is located in the N-terminal section, while the second is found in the central part of the protein sequence. We also developed a profile that covers the entire acylphosphatase-like domain.