@article{mbs:/content/journal/micro/10.1099/00221287-138-9-1935, author = "Pamula, F. and Wheldrake, J. F.", title = "The effect of AMP on the NAD-dependent glutamate dehydrogenase during activation and morphogenesis in the cellular slime moulds", journal= "Microbiology", year = "1992", volume = "138", number = "9", pages = "1935-1940", doi = "https://doi.org/10.1099/00221287-138-9-1935", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-138-9-1935", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "In extracts from vegetative Dictyostelium discoideum V12 the basal NAD-dependent glutamate dehydrogenase (NAD-GDH) activity was low, but it increased on standing at 4°C. When 0.1 mM-AMP was included in the assay mix, enzyme activity was stimulated nearly 30-fold. As the extract was allowed to age, the enzyme rapidly lost its ability to be stimulated by AMP. The response of NAD-GDH to AMP was also dependent on the stage of morphogenesis. The ratios of NAD-GDH activity assayed with and without AMP (+AMP/-AMP ratios) in freshly prepared extracts from cells at 0, 4, 8 and 12 h of development were similar, but declined later in morphogenesis. The + AMP/-AMP ratio decreased sharply during activation at 4°C in extracts from cells at 0, 4, 16 and 20 h of development. By contrast, extracts from cells starved for 8 and 12 h remained more responsive to AMP throughout activation. Analysis of Western blots showed that vegetative NAD-GDH did not undergo any detectable proteolytic cleavage during 96 h of activation at 4°C. Also, no change in molecular mass appeared to take place within the cells until culmination (20–24 h), when some breakdown products appeared. Activation of NAD-GDH also occurred in D. discoideum strains NC4 and AX3, and in D. mucoroides. In addition, the enzyme from these four strains was stimulated by AMP and the + AMP/-AMP ratio declined with similar kinetics during activation. The enzyme from Polysphondylium violaceum was not activated on standing, but it was stimulated by AMP. The effect of activation of NAD-GDH is discussed in relation to a postulated catabolic role for this enzyme.", }