Glutamine Phosphoribosyl Pyrophosphate Amidotransferase From Bacillus Subtilis: Iron-Sulfur Biochemistry and Enzymology

The iron-sulfur prosthetic group of glutamine PRPP amidotransferase was found to be a {4Fe-4S} cluster. In the native enzyme, the cluster exists in the diamagnetic +2 redox state. Treatment of the cluster with oxidants resulted either in no reaction or in oxidative dissolution of the cluster, i.e., a +3 state was not detected. The cluster was reduced poorly with sodium dithionite, but was reduced readily by photoreduction with 5-deazaflavin. Photoreduction of the native enzyme resulted in formation of the +1 redox state of the cluster. The reduced enzyme was EPR silent. Examination of the reduced enzyme by Mossbauer spectroscopy indicated the presence of multiple unpaired electrons (S (GREATERTHEQ) 3/2). The E(,m) of the +1/+2 couple was determined to be (LESSTHEQ) -620 mV. The reduced enzyme was found to be active in the following assays: glutamine PRPP amidotransferase, glutaminase and PRPP hydrolase; these results demonstrated that the cluster does not have a redox function during catalysis of amide transfer by the enzyme.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biochemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Vollmer, Steven John

• Chemistry, Biochemistry

Identifier

(UMI)AAI8410066

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70533