Characterisation of a bis(5'-nucleosidyl) triphosphate pyrophosphohydrolase from encysted embryos of the brine shrimp Artemia.
1. A P1,P3-bis(5'-nucleosidyl)triphosphate pyrophosphohydrolase (Np3 Nase) has been partially purified from Artemia embryos. 2. The Np3 Nase has a native Mr of 115,000 and preferentially hydrolyses substrates of the form Np3 N. Relative rates of hydrolysis are Ap3A (Vrel = 1.0), Gp3G (Vrel = 0.71), Ap4A (Vrel = 0.08), Ap5A (Vrel = 0.09), Gp4G (Vrel = 0.3) and Gp5G (Vrel = 0.33). An NMP is always one of the products. 3. The Km values for Ap3A and Gp3G are 15 and 10 microM respectively. 4. Mg2+, Mn2+ and Ca2+ ions all stimulate the activity, while Zn2+, Co2+ and Ni2+ ions are inhibitory. 5. The activity of the Np3 Nase remains constant during pre-emergence development of encysted embryos but decreases slightly after hatching.
Prescott
M
M
Department of Biochemistry, University of Liverpool, U.K.
Thorne
N M
NM
Milne
A D
AD
McLennan
A G
AG
D017766:Acid Anhydride Hydrolases; D000818:Animals; D001156:Artemia / Q000196:embryology / Q000201:enzymology*; D002413:Cations, Divalent; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature; D000099170:Bis(5'-adenosyl)triphosphatase
D017766:Acid Anhydride Hydrolases; D002413:Cations, Divalent; D010744:Phosphoric Monoester Hydrolases; D000099170:Bis(5'-adenosyl)triphosphatase