Title

31P ENDOR Studies of Xanthine Oxidase: Coupling of Phosphorus of the Pterin Cofactor to Molybdenum(V)

Document Type

Article

Language

eng

Format of Original

7 p.

Publication Date

4-1991

Publisher

American Chemical Society

Source Publication

Biochemistry

Source ISSN

0006-2960

Original Item ID

doi: 10.1021/bi00230a024

Abstract

31P ENDOR spectra are described for three different molybdenum(V) species in reduced xanthine oxidase samples. The spectra were not affected by removing the FAD from the enzyme, implying that this is located at some distance from molybdenum. Furthermore, in confirmation of the work of J. L. Johnson, R. E. London, and K. V. Rajagopalan [(1989) Proc. Natl. Acad. Sci. U.S.A. 86, 6493-6497], NMR and chemical analysis of the phosphate content of highly purified xanthine oxidase showed there are only three phosphate residues per subunit of the enzyme. It is concluded that the ENDOR features are due to hyperfine coupling of the phosphate group of the pterin cofactor to the molybdenum atom. Evaluation of the dipolar component of the coupling has permitted estimation of the molybdenum-phosphorus distances as 7-12 Å. This implies that the cofactor is in an extended conformation in the enzyme molecule. Less detailed 31P ENDOR data on sulfite oxidase are consistent with a similar conformation for the cofactor in this enzyme.

Comments

Biochemistry, Vol. 30, No. 16 (April 1991): 3969-3975. DOI.

Brian Bennett was affiliated with University of Sussex at the time of publication.