Arsenite enzyme interactions

In this section are described the important chemical features of those substrates which are oxidized by the molybdenum hydroxylases. Although these enzymes, particularly aldehyde oxidase, also catalyse numerous reductive reactions under anaerobic conditions in vitro, it has not yet been established whether they occur under physiological conditions and there are as yet insufficient examples of any one reduction reaction to permit any conclusions regarding the structure of substrates. Thus, such reactions will not be discussed here (see [11] and references therein). Properties of those inhibitors which bind at the Mo centre and are also substrate analogues will also be included. However, the interaction of inhibitors such as cyanide and arsenite with the molybdenum hydroxylases and the mechanism of action of the specific xanthine oxidase inhibitor, allo-purinol, have been comprehensively described elsewhere [8, 12, 14, 157]. 

This relationship is sometimes obscured by the interaction of other factors (Barker and Mapson, 1952), and such evidence implies that the connection between these two substances is not direct. A connection between the level of sucrose and ascorbic acid has also been emphasized in experiments in which detached leaves have been treated with several enzymic poisons (Mapson and Barker, 1948). Ascorbic acid disappears from detached leaves when these are supplied with solutions of iodoacetate, fluoride, or arsenite. In each case the disappearance of ascorbic acid was preceded by a parallel fall of sucrose. It is clearly too soon to speculate... 

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