Optical and electron paramagnetic resonance spectroscopic studies on purine hydroxylase II from Aspergillus nidulans.

Journal Article (Journal Article)

Purine hydroxylase II from Aspergillus nidulans contains a molybdenum cofactor very similar to that found in a number of other molybdenum-containing hydroxylases. (A. nidulans contains two purine hydroxylases, I and II, related to each other by possession of a common cofactor and overlapping substrate specificity.) Addition of reducing substrates effects bleaching of the visible absorption spectrum of the enzyme, the decrease in absorbance at 450 nm being linearly proportional to that at 550 nm. No increase in absorption at longer wavelengths was observed during such titrations. Electron paramagnetic resonance studies of reduced samples of native and modified enzyme species showed the presence of a number of Mo(V) signals (gav = 1.97), exhibiting H hyperfine coupling, comparable to those in the corresponding enzymes from other sources. The enzyme possesses two non-heme-iron-sulfur centers, one (Fe2S2)I with gav less than 2.0 and the other (Fe2S2)II with gav greater than 2.0. The flavin radical signal observed at pH 7.8 had a linewidth of 1.5 mT, indicating it to be the anionic form FAD- . In this respect purine hydroxylase II is unique among all molybdenum-containing hydroxylases studied to date.

Full Text

Duke Authors

Cited Authors

  • Coughlan, MP; Mehra, RK; Barber, MJ; Siegel, LM

Published Date

  • March 1, 1984

Published In

Volume / Issue

  • 229 / 2

Start / End Page

  • 596 - 603

PubMed ID

  • 6322698

International Standard Serial Number (ISSN)

  • 0003-9861

Digital Object Identifier (DOI)

  • 10.1016/0003-9861(84)90192-9


  • eng

Conference Location

  • United States