Characterization of the Coral Allene Oxide Synthase Active Site with UV−Visible Absorption, Magnetic Circular Dichroism, and Electron Paramagnetic Resonance Spectroscopy: Evidence for Tyrosinate Ligation to the Ferric Enzyme Heme Iron

Coral allene oxide synthase (AOS), a hemoprotein with weak sequence homology to catalase, is the N-terminal domain of a naturally occurring fusion protein with an 8R-lipoxygenase. AOS converts 8R-hydroperoxyeicosatetraenoic acid to the corresponding allene oxide. The UV−visible absorption and magnet...

Full description

Saved in:

Bibliographic Details
Published in:	Biochemistry (Easton) Vol. 40; no. 7; pp. 2251 - 2259
Main Authors:	Abraham, Biji D, Sono, Masanori, Boutaud, Olivier, Shriner, Anthony, Dawson, John H, Brash, Alan R, Gaffney, Betty J
Format:	Journal Article
Language:	English
Published:	United States American Chemical Society 20-02-2001
Subjects:	Animals Azides - metabolism Binding Sites Catalase - chemistry Cattle Circular Dichroism Cnidaria - enzymology Cyanides - metabolism Electron Spin Resonance Spectroscopy - methods Ferric Compounds - chemistry Ferric Compounds - metabolism Ferrous Compounds - chemistry Fluorides - metabolism Free Radicals - chemistry Free Radicals - metabolism Heme - chemistry Heme - metabolism Intramolecular Oxidoreductases - chemistry Intramolecular Oxidoreductases - metabolism Iron - chemistry Iron - metabolism Ligands Peracetic Acid - chemistry Spectrophotometry, Ultraviolet - methods Tyrosine - chemistry Tyrosine - metabolism
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Coral allene oxide synthase (AOS), a hemoprotein with weak sequence homology to catalase, is the N-terminal domain of a naturally occurring fusion protein with an 8R-lipoxygenase. AOS converts 8R-hydroperoxyeicosatetraenoic acid to the corresponding allene oxide. The UV−visible absorption and magnetic circular dichroism spectra of ferric AOS and of its cyanide and azide complexes, and the electron paramagnetic resonance spectra of native AOS (high-spin, g = 6.56, 5.22, 2.00) and of its cyanide adduct (low-spin, g = 2.86, 2.24, 1.60) closely resemble the corresponding spectra of bovine liver catalase (BLC). These results provide strong evidence for tyrosinate ligation to the heme iron of AOS as has been established for catalases. On the other hand, the positive circular dichroism bands in the Soret region for all three derivatives of ferric AOS are almost the mirror image of those in catalase. In addition, the cyanide affinity of native AOS (K d = 10 mM at pH 7) is about 3 orders of magnitude lower than that of BLC. Thus, while these results conclusively support a common tyrosinate-ligated heme in AOS as in catalase, significant differences exist in the interaction between their respective heme prosthetic groups and protein environments, and in the access of small molecules to the heme iron.
Bibliography:	ark:/67375/TPS-1B7M510G-X This research was supported by National Institutes of Health Grants GM-26730 and RR-03960 (to J.H.D.) and GM-53638 (to A.R.B.) and GM-36232 (to B.J.G.). The electromagnet for the Jasco J-500 spectrometer was obtained with a grant from the Research Corp. (to J.H.D.). istex:A8EE7E78B4D1D7C24996D66EBC32C9A520B84ADA ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0006-2960 1520-4995
DOI:	10.1021/bi002121h