ATP sulfurylase from trophosome tissue of Riftia pachyptila (hydrothermal vent tube worm)

摘要: Abstract ATP sulfurylase (ATP: sulfate adenylyltransferase, EC 2.7.7.4) was extensively purified from trophosome tissue of Riftia pachyptila, a tube worm that thrives in deep ocean hydrothermal vent communities. The enzyme is probably derived the sulfide-oxidizing bacteria densely colonize tissue. Glycerol (20% v ) protected against inactivation during purification and storage. native appears to be dimer (MW 90 kDa ± 10%) composed identical size subunits 48 5%). At pH 8.0, 30 †C, specific activities (units × mg protein−1) most highly sample are as follows: synthesis, 370; APS 23; molybdolysis, 65; APSe synthesis or selenolysis, 1.9. Km values for PPi at 5 m Mg2+ 6.3 14 μ , respectively. In direction, MgATP SO42− 1.7 27 MoO42− molybdolysis reaction 80 150 Kia 0.65 . potent inhibitor competitive with both (Kiq = 2.2 μM). However, (+ Mg2+) virtually inactive inhibitor. Oxyanion dead end inhibitors include (in order decreasing potency) ClO4− > FSO3− (Ki 22 μM) ClO3− NO3− S2O32− (Ki's 43 M). uncompetitive MgATP, but noncompetitive. Each subunit contains two free SH groups, least one which functionally essential. ATP, SO42−, MoO42−, each protect by excess 5,5′-dithiobis-(2-nitrobenzoate). ineffective protector unless present. (+Mg2+) does not inactivation. little no “ADP sulfurylase.” high level (67–176 units g fresh wt −1 four different specimens, corresponding 4–10 sites), Kcat (296 s−1), Km's consistent role formation sulfide oxidation, i.e., physiological + MgPPi ⇄ MgATP.