Sulfate-activating enzymes of Penicillium chrysogenum. The ATP sulfurylase.adenosine 5'-phosphosulfate complex does not serve as a substrate for adenosine 5'-phosphosulfate kinase.
At a noninhibitory steady state concentration of adenosine 5'-phosphosulfate (APS), increasing the concentration of Penicillium chrysogenum ATP sulfurylase drives the rate of the APS kinase-catalyzed reaction toward zero. The result indicates that the ATP sulfurylase.APS complex does not serve as a substrate for APS kinase, i.e. there is no "substrate channeling" of APS between the two sulfate-activating enzymes. APS kinase had no effect on the [S]0.5 values, nH values, or maximum isotope trapping in the single turnover of ATP sulfurylase-bound [35S]APS. Equimolar APS kinase (+/- MgATP or APS) also had no effect on the rate constants for the inactivation of ATP sulfurylase by phenylglyoxal, diethylpyrocarbonate, or N-ethylmaleimide. Similarly, ATP sulfurylase (+/- ligands) had no effect on the inactivation of equimolar APS kinase by trinitrobenzene sulfonate, diethylpyrocarbonate, or heat. (The last promotes the dissociation of dimeric APS kinase to inactive monomers.) ATP sulfurylase also had no effect on the reassociation of APS kinase subunits at low temperature. The cumulative results suggest that the two sulfate activating enzymes do not associate to form a "3'-phosphoadenosine 5'-phosphosulfate synthetase" complex.
Renosto
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Department of Biochemistry and Biophysics, University of California, Davis 95616.
Martin
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Segel
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D000249:Adenosine Monophosphate / Q000031:analogs & derivatives*; D000250:Adenosine Phosphosulfate / Q000378:metabolism*; D007700:Kinetics; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010407:Penicillium / Q000201:enzymology*; D010408:Penicillium chrysogenum / Q000201:enzymology*; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D017853:Phosphotransferases (Alcohol Group Acceptor); D013379:Substrate Specificity; D013430:Sulfate Adenylyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D013462:Sulfur Radioisotopes
D013462:Sulfur Radioisotopes; D000249:Adenosine Monophosphate; D000250:Adenosine Phosphosulfate; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C019617:adenylylsulfate kinase; D009713:Nucleotidyltransferases; D013430:Sulfate Adenylyltransferase