Human metastasis regulator protein H-prune is a short-chain exopolyphosphatase.

The DHH superfamily human protein h-prune, a binding partner of the metastasis suppressor nm23-H1, is frequently overexpressed in metastatic cancers. From an evolutionary perspective, h-prune is very close to eukaryotic exopolyphosphatases. Here, we show for the first time that h-prune efficiently hydrolyzes short-chain polyphosphates (k cat of 3-40 s (-1)), including inorganic tripoly- and tetrapolyphosphates and nucleoside 5'-tetraphosphates.

Kinetic and mutational analyses of the major cytosolic exopolyphosphatase from Saccharomyces cerevisiae.

Yeast exopolyphosphatase (scPPX) processively splits off the terminal phosphate group from linear polyphosphates longer than pyrophosphate. scPPX belongs to the DHH phosphoesterase superfamily and is evolutionarily close to the well characterized family II pyrophosphatase (PPase). Here, we used steady-state kinetic and binding measurements to elucidate the metal cofactor requirement for scPPX catalysis over the pH range 4.

A trimetal site and substrate distortion in a family II inorganic pyrophosphatase.

We report the first crystal structures of a family II pyrophosphatase complexed with a substrate analogue, imidodiphosphate (PNP). These provide new insights into the catalytic reaction mechanism of this enzyme family. We were able to capture the substrate complex both by fluoride inhibition and by site-directed mutagenesis providing complementary snapshots of the Michaelis complex.

Oxidation of the cyanobacterial hepatotoxin microcystin-LR by chlorine dioxide: influence of natural organic matter.

Cyanobacteria (blue-green algae) are known producers of cytotoxic, hepatotoxic, and neurotoxic compounds with severe acute and chronic effects on vertebrates. Successful removal of these toxins in drinking water treatment is therefore of importance for public health. In the present work the oxidation of the cyanobacterial hepatotoxin microcystin-LR (MC-LR) by chlorine dioxide (ClO2) was studied at natural microcystin concentrations (10 microg L(-1)) and normal ClO2 dosages (1 mg L(-1)) in the absence and presence of natural organic matter (NOM).

An unusual, His-dependent family I pyrophosphatase from Mycobacterium tuberculosis.

Soluble inorganic pyrophosphatases (PPases) comprise two evolutionarily unrelated families (I and II). These two families have different specificities for metal cofactors, which is thought to be because of the fact that family II PPases have three active site histidines, whereas family I PPases have none. Here, we report the structural and functional characterization of a unique family I PPase from Mycobacterium tuberculosis (mtPPase) that has two His residues (His21 and His86) in the active site.

Effects of active site mutations on the metal binding affinity, catalytic competence, and stability of the family II pyrophosphatase from Bacillus subtilis.

Family II inorganic pyrophosphatases (PPases) have been recently found in a variety of bacteria. Their primary and tertiary structures differ from those of the well-known family I PPases, although both have a binuclear metal center directly involved in catalysis. Here, we examined the effects of mutating one Glu, four His, and five Asp residues forming or close to the metal center on Mn(2+) binding affinity, catalysis, oligomeric structure, and thermostability of the family II PPase from Bacillus subtilis (bsPPase).

Site-specific effects of zinc on the activity of family II pyrophosphatase.

Family II pyrophosphatases (PPases), recently found in bacteria and archaebacteria, are Mn(2+)-containing metalloenzymes with two metal-binding subsites (M1 and M2) in the active site. These PPases can use a number of other divalent metal ions as the cofactor but are inactive with Zn(2+), which is known to be a good cofactor for family I PPases. We report here that the Mg(2+)-bound form of the family II PPase from Streptococcus gordonii is nearly instantly activated by incubation with equimolar Zn(2+), but the activity thereafter decays on a time scale of minutes.