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Mammalian Cell Physiology
Published in Anthony S. Lubiniecki, Large-Scale Mammalian Cell Culture Technology, 2018
Like glucose, the metabolism of glutamine is also accelerated in rapidly growing cells (55, 56, 64, 70, 71, 73, 136–139, 142, 146–148). This pattern of elevated glutamine utilization in fast-growing cells has been termed "glutaminolysis" by McKeehan (151, 163). The uptake and metabolism of glutamine increases eightfold in mitogenically stimulated thymocytes (56). Lymphocytes increase their metabolism of glutamine in response to an immune stimulus prior to undergoing a rapid increase in cell division and protein synthesis (146, 147). The major end products of glutamine metabolism are generally CO2, ammonia, lactate, glutamate, aspartate, and alanine. The relative concentrations of these metabolites will depend on the metabolic needs of a given cell population and probably on the cell enzymology.
Catabolite Regulation of the Main Metabolism
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
The growth of Human tumor cells is driven by MYC oncogene, and sensitive to glutamin (Gln) metabolism or glutaminolysis (Yuneva et al. 2007), where glutamin transported by glutamine transporter is converted to glutamate (Glu) by glutaminase, and in turn glutamate is converted to αKG in the TCA cycle. In this reaction, NADPH and NH3 are produced, where NH3 is excreted as waste. Lipid synthesis is made from citrate in the proliferating cell, where OAA is limiting for citrate formation, and thus OAA must be replenished by anaplerosis. Although Pyc may play a role for this, it may be minor. Instead, the glutamine-dependent anaplerosis plays an important role. As mentioned above, glutamine can be converted to αKG in the cytosol as well as in the mitochondria, and αKG in the cytosol can enter into the mitochondria. The mitochondrial glutamate can be converted to αKG by glutamate dehydrogenase (GDH). This αKG is converted to replenish OAA via part of the TCA cycle. Glutamine carbon is converted to lactate by glutaminolysis (deBerardinis et al. 2008). In the case where glutamine is limited, the anaplerosis by the above pathway is limited, and the anaplerosis is mainly made by Pyc from glucose (Cheng et al. 2011).
Epigenetic and Metabolic Alterations in Cancer Cells: Mechanisms and Therapeutic Approaches
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
An alteration in cellular metabolism is a fundamental property of cancer cells that enables them to meet the high metabolic demands of continued proliferation, despite the limited resources within the hostile tumor microenvironment (Hsu and Sabatini, 2008). Tumor cells utilize glycolysis to meet most of their increased requirement for ATP, without increasing 02 consumption and oxidative phosphorylation. This in turn converts most of the consumed glucose into lactate, which itself is a relatively inefficient process (2 ATP per glucose) but has a rapid turnover and provide substrates for other biosynthetic reactions. As a consequence, tumor cells are reliant on a steady supply of glucose for growth and are frequently addicted to this nutrient (Shaw, 2006). Apart from glucose, cancer cells are also dependent on a robust supply of reduced nitrogen for the biosynthesis of amino acids and nucleotides, building blocks for proteins and DNA/RNA, respectively. Recent metabolic studies revealed that tumor cells depend heavily on the supply of glutamine for nitrogen anabolism (Wise and Thompson, 2010). Glutamine, the most abundant amino acid in the blood circulation, is metabolized in cancer cells via glutaminolysis. Glutaminolysis replenishes TCA cycle, provides biosynthetic precursors for nucleotide and protein biosynthesis, and generates reducing potential for maintaining redox homeostasis (Son et al., 2013; Wise et al., 2008). Apart from glutamine and glucose, recent studies revealed that cancer cells has deregulated fatty acid and cholesterol metabolism in order to sustain their high proliferative demands. In small subsets of cancer types, mutations in metabolic genes can lead to abnormal accumulation of endogenous cancer-promoting metabolites or even novel oncometabolites that drives tumorigenesis. Hence, cancer cells have acquired diverse strategies to highjack metabolic pathways to sustain their survival and growth.
Glutaminase-free L-asparaginase production by Leucosporidium muscorum isolated from Antarctic marine-sediment
Published in Preparative Biochemistry & Biotechnology, 2021
Rominne Karla Barros Freire, Carlos Miguel Nóbrega Mendonça, Rafael Bertelli Ferraro, Ignacio Sánchez Moguel, Aldo Tonso, Felipe Rebello Lourenço, João Henrique Picado Madalena Santos, Lara Durães Sette, Adalberto Pessoa Junior
In this work, quantitative analysis of ASNase production pointed L. muscurum CRM 1648 as the most producer strain (490.41 U L−1), resulting in a volumetric productivity of 5.12 U L−1 h−1. Besides, extracellular enzyme and glutaminolysis activity was not detected for any strain. As glutaminolysis activity is responsible for neurotoxic and hepatotoxic effects in leukemic patients treated with ASNase, glutaminase-free ASNase could be a better alternative for ALL treatment. Glutaminase-free ASNase was reported in Pseudomonas spp.,[45]Bacillus spp.[46] and fungal endophytes.[47] Extracellular ASNase was also detected in Bacillus spp.,[48] species of actinomycetes[49] and Aspergillus spp.[50] However, there are few reports on yeasts producing ASNase. Saccharomyces cerevisiae was found to produce two types of ASNases, a periplasmatic one (ASP3) whose production is stimulated by nitrogen starvation, and an intracellular and constitutive enzyme (ASP1).[25]Candida utilis seems to produce a periplasmatic ASNase, similar to ASP3, and is able to use both L-asparagine and D-asparagine as a substrate.[22,51] ASNase produced by Rhodosporidium toruloides is periplasmatic and has a homodimeric structure.[24] Yeasts present in Antarctic marine sediments are subjected to low temperatures and higher atmospheric pressure than at sea level, for that reason adaptation mechanisms are seen as a way to survive in those harsh conditions. The production of glutaminase free ASNase could be an adaptive trait for those yeasts, in fact, another recent study also ascertains the presence of extremophiles yeasts from Antarctic region capable of producing glutaminase and urease free ASNase, supporting the possible adaptation mechanism in these inhospitable regions.[52]