Regulation of inorganic sulfate activation in filamentous fungi. Allosteric inhibition of ATP sulfurylase by 3'-phosphoadenosine-5'-phosphosulfate.

摘要: ATP sulfurylases from Penicillium chrysogenum, duponti, Aspergillus nidulans, and Neurospora crassa are strongly inhibited by 3'-phosphoadenosine-5'-phosphosulfate (PAPS), the product of second (adenosine-5'-phosphosulfate kinase-catalyzed) reaction in two-step activation inorganic sulfate. The v versus [PAPS] plots sigmoidal. At physiological concentrations MgATP (0.17-3 mM) SO4(2-) (0.4-10 mM), [I]0.5 for PAPS inhibition P. chrysogenum enzyme is 35-200 microM; [I]0.9 68-310 microM. In presence PAPS, [S]0.5 values both substrates increased [MgATP] [SO4(2-)] or [MoO4(2-)] Fluorosulfonate (FSO3-) thiosulfate (S2O3(2-] (non-reactive sulfate analogs) inhibit at subsaturating substrate absence but low analogs activate when present. Thus, behaves as an allosteric inhibitor sulfurylase. contrast, adenosine-5'-phosphosulfate (APS = Q), immediate SO4(2-)-dependent reaction, a linear enzyme, competitive with MoO4(2-) (Kiq 36-73 nM). FSO3- S2O3(2-) does not APS. effect on fungal sulfurylase very similar to that observed single highly reactive cysteinyl SH group/subunit (SH-1) covalently modified (Renosto, F., Martin, R. L., Segel, I. H. (1987) J. Biol. Chem. 262, 16279-16288). results suggest vitro SH-1 modification induces conformational change mimics induced vivo reversible binding PAPS. No evidence was obtained modifies SH-1. rat liver (Yu, M., Jain, S., Chen, L. T., (1989) Arch. Biochem. Biophys. 269, 156-174), spinach leaf, cabbage Saccharomyces cerevisiae do display sigmoidal initial velocity contain residue whose curves. may be part sequential feedback process unique group organisms use two diverging pathways, reductive assimilation ester formation.