ABSTRACT
In 1988 Kishore and Shah (1988) wrote that ''very little information is available on the reactions and enzymology of histidine biosynthesis in plants" and concluded that studies of the pathway "may lead to an understanding of regulation of L-histidine biosynthesis in plants and facilitate the design of new herbicides." Imidazole glycerol phosphate dehydratase (IGPD; EC 4.2.1.19) has long been implicated in the mode of action of the herbicide 3-amino-I,2,4-triazole (amitrole); however, little was known about the plant enzyme, and the evidence for this mode of action was by no means conclusive. In the last decade, IGPD and histidinol dehydrogenase (HDH; EC 1.1.1.23) have attracted significant attention in the design of novel herbicides and the research that this has stimulated has greatly increased our knowledge about these particular enzymes. The existence of ATP phosphoribosylttansfcrasc (ATP-PRT; EC 2.4.2.17), histidinol phosphate phosphatase (EC 3.1.3.15; Wiater et aI. 1971a), and probably, imidazole acetol phosphate aminotransferase (EC 2.6.1.9; Negrutiu et aI. 1985) has also been demonstrated in plants. A general review of histidine biosynthesis in plants is provided in Chapter 10. In this chapter we have concentrated on just three CDZymes: ATP-PRT, IGPD, and HDH, because these have been the subject of research relevant to the discovery of novel herbicides.
