The pyridine nucleotide cycle is a network of salvage and recycling routes maintaining homeostasis of NAD(P) cofactor pool in the cell. Nicotinamide mononucleotide (NMN) deamidase (EC 3.5.1.42), one of the key enzymes of the bacterial pyridine nucleotide cycle, was originally described in Enterobacteria, but the corresponding gene eluded identification for over 30 years. A genomics-based reconstruction of NAD metabolism across hundreds of bacterial species suggested that NMN deamidase reaction is the only possible way of nicotinamide salvage in the marine bacterium Shewanella oneidensis. This prediction was verified via purification of native NMN deamidase from S. oneidensis followed by the identification of the respective gene, termed pncC. Enzymatic characterization of the PncC protein, as well as phenotype analysis of deletion mutants, confirmed its proposed biochemical and physiological function in S. oneidensis. Of the three PncC homologs present in Escherichia coli, NMN deamidase activity was confirmed only for the recombinant purified product of the ygaD gene. A comparative analysis at the level of sequence and three-dimensional structure, which is available for one of the PncC family member, shows no homology with any previously described amidohydrolases. Multiple alignment analysis of functional and nonfunctional PncC homologs, together with NMN docking experiments, allowed us to tentatively identify the active site area and conserved residues therein. An observed broad phylogenomic distribution of predicted functional PncCs in the bacterial kingdom is consistent with a possible role in detoxification of NMN, resulting from NAD utilization by DNA ligase.The pyridine nucleotide cycle (PNC) 3 is a network of biochemical transformations that allow cells to recycle the by-products of endogenous NAD consumption back to the coenzyme and to salvage the available pyridine bases, nucleosides, and nucleotides as NAD precursors. The importance of NAD regeneration through recycling pathways is emphasized by the occurrence of an intense nonredox NAD consumption as suggested by the rapid turnover of the coenzyme pool within the cell (1). In bacteria, the pyridine by-products of the NADconsuming enzymes NMN and Nm can be recycled back to NAD through the PNC depicted in Fig. 1 (2, 3). Briefly, Nm can be converted to NAD through two different routes. The most commonly occurring pathway is initiated by Nm deamidation to Na, followed by Na conversion to NaMN, NaMN adenylation to NaAD, and NaAD amidation to NAD. The last three reactions comprise the so-called Preiss-Handler pathway (4, 5). The second Nm recycling route is a relatively rare, nondeamidated pathway, whereby Nm is directly phosphoribosylated to NMN and NMN is then adenylated to NAD. NMN can be recycled back to NAD through two pathways shown to be functional in Escherichia coli and Salmonella typhymurium (6): the predominant route, PNC IV, proceeds via NMN deamidation to NaMN, which is then converted to NAD by entering the PreissHandler pathway; the alternati...
If calls to care for other species multiply in a time of global and local environmental crisis, this article demonstrates that caring practices are not always as benevolent or irenic as imagined. To save endemic tortoises from the menace of extinction, Proyecto Isabela killed more than two hundred thousand goats on the Galápagos Islands in the largest mammal eradication campaign in the world. While anthropologists have looked at human engagements with unwanted species as habitual and even pleasurable, I discuss an exceptional intervention that was ethically inflected toward saving an endemic species, yet also controversial and distressing. Exploring eradication’s biological, ecological, and political implications and discussing opposing practices of care for goats among residents, I move past the recognition that humans live in a multispecies world and point to the contentious nature of living with nonhuman others. I go on to argue that realizing competing forms of care may help conservation measures—and, indeed, life in the Anthropocene—to move beyond the logic of success and failure toward an open-ended commitment to the more-than-human.
Drawing on ethnographic fieldwork, this essay examines how the local Jehovah’s Witnesses’ response to the current ecological crisis on the Galápagos Islands has produced a distinct form of religious environmentalism. Specifically, I argue that the Jehovah’s Witnesses’ vision of the ultimate future informs action rather than despair—contrary to what is often assumed about millenarian beliefs. This essay joins voices in Christian feminist and eco-theology interested in reclaiming eschatology for its imaginative valence. Yet, unlike invocations for hope that lack consideration of their viability, my ethnographic approach contributes to this literature with a view of the practical reverberations of eschatology. Further, current discussions about ecological unraveling, often couched around the concept of the Anthropocene, have reinforced expert-driven, techno-scientific measures that exclude other forms of knowledge production and practical interventions. If such worries continue to motivate a paradigm of conservation that exclude locals, my essay shows how the local Jehovah’s Witnesses promote a valuable alternative form of environmentalism, on the Galápagos and elsewhere.
In 1959, the Charles Darwin Station and the Galápagos National Park were established, formally inaugurating conservation on the archipelago. In the same year, a utopian colony from the United States arrived. Whereas scholars have dismissed the latter and focused on the former, this essay unveils the science-inspired utopianism common to both enterprises. Investing science with the exclusive role of producing all knowledge and steering politics, leaders of the two initiatives aspired not only to protect nature but also to forge a new humanity. Describing how such ambitions burst along lines of race, class, and nationality, I argue that these enterprises consolidated the current understanding of the Galápagos as “pristine”: a site fit for research and tourism but unhospitable to (other) people. Drawing on archival and historical documents, this essay aims to reinvigorate two conversations: one between science and technology studies (STS) and conservation, and the other between STS and utopian studies. If recent attempts at bridging the divide between science and imagination have emphasized how powerful actors shape human society, this essay considers the long-lasting effects of scientific imaginaries on a politics of nature.
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