Role of Mo-C bonds in xanthine oxidase action.

Introduction It is now appropriate to discuss fine details of the mechanism of action of xanthine oxidase because of the extensive spectroscopic and kinetic evidence available; this is especially so since this has recently been supplemented by X-raycrystallographic data. Much of the information has been reviewed comprehensively [1,2] and is also discussed in this volume [3,4]. In this article we intend to concentrate on the role of electron nuclear double resonance (ENDOR) spectroscopy in determining aspects of the structure of intermediates in the mechanism, with particular reference to details of the evidence for Mo-C bonds, since there may be misunderstandings in the literature concerning how we interpreted our results [S]. We go on to consider some of the various hypotheses concerning the mechanisms that are currently being debated.