Kinetic properties of ATP sulfurylase and APS kinase from Thiobacillus denitrificans.
The Thiobacillus denitrificans genome contains two sequences corresponding to ATP sulfurylase (Tbd_0210 and Tbd_0874). Both genes were cloned and expressed protein characterized. The larger protein (Tbd_0210; 544 residues) possesses an N-terminal ATP sulfurylase domain and a C-terminal APS kinase domain and was therefore annotated as a bifunctional enzyme. But, the protein was not bifunctional because it lacked ATP sulfurylase activity. However, the enzyme did possess APS kinase activity and displayed substrate inhibition by APS. Truncated protein missing the N-terminal domain had <2% APS kinase activity suggesting the function of the inactive sulfurylase domain is to promote the oligomerization of the APS kinase domains. The smaller gene product (Tbd_0874; 402 residues) possessed strong ATP sulfurylase activity with kinetic properties that appear to be kinetically optimized for the direction of APS utilization and ATP+sulfate production, which is consistent with an enzyme that functions physiologically to produce inorganic sulfate.
Gay
Sean C
SC
Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
Fribourgh
Jennifer L
JL
Donohoue
Paul D
PD
Segel
Irwin H
IH
Fisher
Andrew J
AJ
D003001:Cloning, Molecular; D015870:Gene Expression; D007700:Kinetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013430:Sulfate Adenylyltransferase / Q000737:chemistry* / Q000235:genetics; D013855:Thiobacillus / Q000201:enzymology* / Q000235:genetics
D017853:Phosphotransferases (Alcohol Group Acceptor); C019617:adenylylsulfate kinase; D013430:Sulfate Adenylyltransferase