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Regulation of Enzymatic Activity
Published in D. B. Keech, J. C. Wallace, Pyruvate Carboxylase, 2018
The chief function of pyruvate carboxylase in cells of the liver, kidney, and adipose tissue appears to be the synthesis of oxaloacetate in an anaplerotic reaction which provides intermediates of the citric acid cycle for a number of biosynthetic pathways460 (Figure 16 and Chapter 2, Section I), It is likely that pyruvate carboxylase also has an anaplerotic function in the liver, kidney, and adipose tissue79,750 in addition to its major roles in gluconeogenesis and lipogenesis.
MUSCLE METABOLISM
Published in David M. Gibson, Robert A. Harris, Metabolic Regulation in Mammals, 2001
David M. Gibson, Robert A. Harris
This is an example of an anaplerotic reaction, defined as a reaction that results in net production of an intermediate of the citric acid cycle. Such reactions that replenish the citric acid cycle are readily identified by the appearance of a citric acid cycle intermediate on the right-hand side of the equation. The involvement of citric acid cycle intermediates on both sides of the equation disqualifies the reaction as anaplerotic, e.g. the reaction catalyzed by aspartate aminotransferase above. The reaction catalyzed by the biotin-dependent enzyme pyruvate carboxylase is another example of anaplerosis:
Tao-Hong-Si-Wu decoction improves depressive symptoms in model rats via amelioration of BDNF-CREB-arginase I axis disorders
Published in Pharmaceutical Biology, 2022
Xiaoping Zhang, Zeng Li, Chuanpu Shen, Jinzhi He, Longfei Wang, Lei Di, Bin Rui, Ning Li, Zhicheng Liu
The general declines in the levels of AAs (glycine, alanine, proline, phenylalanine, glutamate, lysine and tyrosine) were remarkable features of CUMS. After treatment with TSD, the levels of most AAs recovered in the serum of rats. First, the decreases in the levels of AAs suggested a malnutrition situation in rats with CUMS, which was reported previously (Tan et al. 2016). Such a symptom was evidenced by the weight losses in the model group (Figure 1(a)). The impaired anabolic metabolism could be partly reflected by the lower levels of energetic metabolites such as citrate and lactate in rats with CUMS than in other groups. Notably, common discriminants between M versus B and M versus TSD-treated rats, such as alanine and glutamate, were AAs involved in the anaplerotic reactions from AA to the TCA cycle, which is the core metabolic pathway for energy supply. Second, the amelioration of the defective Tyr/Phe pathway was also found in the TSD-treated rats, which was in accordance with the study by Liu CC et al. (2015). Finally, glycine as well as glutamate, which could be converted into GABA, were associated with neurotransmitters. Thus, besides the diminished secretion of glycine and 5-HT, depressive symptoms in rats with CUMS were firmly attributed to the inhibited transmitter synthesis.
Effects of Citrulline Malate Supplementation on Muscle Strength in Resistance-Trained Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Published in Journal of Dietary Supplements, 2022
Andreo F. Aguiar, Juliano Casonatto
Among NO-precursor supplements, citrulline malate (CM), a combination of citrulline (CIT) with malate in ratios ranging from 1:1 to 2:1 (Trexler et al. 2019) has received great attention from researchers in the last decade. The potential ergogenic effects of CM have been attributed to three key mechanisms. First, CIT ingestion has been shown to increase plasma L-arginine levels (Rougé et al. 2007; Sureda et al. 2010; Thibault et al. 2011). Given that L-arginine is the main substrate for synthesis of NO, it has been proposed that CM supplementation could indirectly increase NO synthesis (Pérez-Guisado and Jakeman 2010) and consequently increase blood flow and improves the supply of oxygen and energy substrates to the active muscles (Joyner and Casey 2015), thereby improving muscle performance. Second, CIT is an essential component of the urea cycle in the liver (Curis et al. 2005), where L-arginine produced from CIT is catabolized by arginase into ornithine and urea. Given that urea is the major vehicle to eliminate ammonia, a promoter of muscle fatigue (Mutch and Banister 1983), it has been suggested that CIT supplementation may improve ammonia homeostasis (Breuillard et al. 2015) and thus improving muscle function. Third, malate is an intermediate of the Krebs cycle, and its greater availability after CM supplementation could increase aerobic ATP production through anaplerotic reactions (Bendahan et al. 2002), resulting in decreased muscle fatigue and improved muscle performance (Bendahan et al. 2002; Pérez-Guisado and Jakeman 2010; Wax et al. 2016).
Long non-coding RNA CCAT2 as a therapeutic target in colorectal cancer
Published in Expert Opinion on Therapeutic Targets, 2018
Johannes Foßelteder, George A. Calin, Martin Pichler
In a recently published study, Redis et al. described a CCAT2-dependent regulation of the cancer energy metabolism via interaction with the splicing process of glutaminase [8]. Overexpression of CCAT2 in CRC cell lines showed higher glucose uptake, lactate secretion, and oxygen consumption in vitro and in vivo by subcutaneous injection into nude mice. Due to the increased metabolic activity, the intermediates of the TCA cycle must be replenished via anaplerotic reactions and glutamine is the main source for that. Glutamine is subsequently deaminated by glutaminase (GLS). Redis et al. showed that glutamine uptake was not altered in CCAT2 overexpressing cells but GLS activity was upregulated. Glycolysis and glutaminolysis are both regulated by MYC, which is a target of CCAT2.Two alternative splicing forms of GLS are known, KGA (glutaminase kidney isoform) and GAC (glutaminase isoform C). GAC has a higher catalytic activity than KGA and therefore may be more relevant for replenishing intermediates of the TCA cycle. GAC expression was upregulated in CCAT2 overexpressing cells and could be shown to promote migration, metastasis, and enhanced energy metabolism. CFIm25 is a subunit of the CFlm complex, which is associated with the GLS splicing. CCAT2 binds CFlm25 and interacts with GLS pre-mRNA, which suggests that CCAT2 enhances the alternative splicing of GLS to GAC. Additionally, MYC acts as transcription factor for CFIm25, which describes another regulatory pathway in this complex network. A complete overview of the above described mechanisms is provided in Figure 1.