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The Bioenergetics of Mammalian Sperm Motility
Published in Claude Gagnon, Controls of Sperm Motility, 2020
In many tissues, glucose 6-phosphate and fructose 1,6-bisphosphate can be hydrolyzed to glucose or fructose 6-phosphate by glucose 6-phosphatase and fructose 1,6-bisphosphatase, respectively. These reactions are integral to gluconeogenesis, but because they occur alongside the corresponding kinase reactions, they permit substrate cycling driven by the conversion of ATP to ADP and Pi (Figure 6). This is often referred to as futile substrate cycling because it consumes ATP to no apparent purpose, but it may have useful physiological roles, e.g., heat production or increasing the sensitivity of metabolic regulation.134,135
Lipids of Dermatophytes
Published in Rajendra Prasad, Mahmoud A. Ghannoum, Lipids of Pathogenic Fungi, 2017
It is the key enzyme in the pathway of phospholipid synthesis and catalyzes the formation of glycerol-3-phosphate from glycerol. Among dermatophytes, this enzyme has been identified and characterized in M. gypseum and E. floccosum.60,61 It was found in cytosolic fraction and was activated and stabilized by ammonium sulfate. Kinetic studies of the enzyme showed that it catalyzed the reaction by ping-pong mechanism,61 as compared to ordered bibi sequential mechanism for C. mycoderma. Two pH optima 8.0 and 10.5 were observed for this enzyme in both M. gypseum and E. floccosum. Glucose-6-phosphate and fructose 1,6-bisphosphate were found to inhibit the enzyme competitively while glucose had no effect on the activity of this enzyme. The molecular weight of this enzyme in M. gypseum was found to be 450 kDa and ATP was the most effective phosphate donor.61
Fish Allergy
Published in Andreas L. Lopata, Food Allergy, 2017
Annette Kuehn, Karthik Arumugam
Enolases and aldolases are key enzymes of the catabolic glycolysis present in all tissues. Aldolase or 40 kDa-fructose-bisphosphate aldolase (EC 4.1.2.13) splits fructose 1,6-bisphosphate into triose phosphates dihydroxyacetone phosphate and glyceraldehyde 3-phosphate (4th step of glycolysis) (Garfinkel and Garfinkel 1985). Enolase or 50 kDa-phosphopyruvate hydratase (EC 4.2.1.11) is a metalloenzyme (Mg2+-ions per molecule) catalysing the conversion of 2-phosphoglycerate to phosphoenolpyruvate (9th step of glycolysis). Both enzymes belong to the structural family of so-called “TIM barrel”-proteins (Kuehn et al. 2016). Eponym for this family is the triosephosphate isomerase (TIM), which was characterized as the first protein by a common structure of eight alpha-helices alternating with eight beta-strands. Despite of the structural homology within this family, there is a lack of substantial sequence identity between TIM barrel-proteins.
Justicia carnea extracts ameliorated hepatocellular damage in streptozotocin-induced type 1 diabetic male rats via decrease in oxidative stress, inflammation and increasing other risk markers
Published in Biomarkers, 2023
John Adeolu Falode, Oluwaseun Igbekele Ajayi, Tolulope Victoria Isinkaye, Akinwunmi Oluwaseun Adeoye, Basiru Olaitan Ajiboye, Bartholomew I. C. Brai
Our study revealed that induction of diabetes with STZ led to a significant (p < 0.05) elevation in the albumin and bilirubin concentrations, while a significant (p < 0.05) decrease was also observed in the hepatic glycogen and insulin concentrations in the diabetic control (STZ) group (Figure 5a–d). Albumin concentration did not differ across all the groups significantly. Whereas, bilirubin concentration in the extract-treated groups did not differ from the control group, while the diabetic-treated groups were not significantly different from the metformin group in both the direct and total bilirubin tests. Similarly, the extract-treated groups, and the treated diabetic groups and metformin group had no significant difference (p < 0.05) in the hepatic glycogen and insulin assays. The activities of fructose-1,6-bisphosphate, glucose-6-phosphatase, and hexokinase were also demonstrated (Figure 5e–g). There was a significant difference (p < 0.05) in the activities of these enzymes between the STZ group and the control, and other groups. The administration of our extracts was able to reduce the activities of fructose-1,6-bisphosphate and glucose-6-phosphatase, and also raise hexokinase activity when compared to the STZ-induced group. There was no significant difference among the extract-treated groups, and the diabetic-treated and the metformin groups across all three enzyme assays.
Glycometabolic rearrangements–aerobic glycolysis in pancreatic ductal adenocarcinoma (PDAC): roles, regulatory networks, and therapeutic potential
Published in Expert Opinion on Therapeutic Targets, 2021
Enhanced glycolysis is well known to be closely associated with resistance to tumor therapy [83]. Many studies have demonstrated a link between enhanced glycolysis and therapy resistance in a variety of cancers, including PDAC [84–87]. Enhanced glycolysis in PDAC was shown to promote resistance to gemcitabine, whereas the application of 2DG, an inhibitor of glycolysis, reversed this effect [87]. According to the published studies, the mechanisms by which aerobic glycolysis influences therapy sensitivity of PDAC can be summarized as follows. (1) HK2, a key enzyme of glycolysis, is induced to dimerize and combine with voltage‐dependent anion channels by ROS derived from gemcitabine, leading to resistance to gemcitabine [88]. (2) Fructose-1,6-bisphosphatase (FBP1), a key enzyme in gluconeogenesis, helps to convert fructose-1,6-bisphosphate to fructose-6-phosphate [18]. Loss of FBP1 in PDAC activates the IQGAP1–extracellular regulatory protein kinase (ERK)–Myc axis, causing resistance to gemcitabine [89]. (3) Upregulation of mucin-1 (MUC1), an oncogene in various cancers and a contributor to glycometabolic rearrangements in PDAC, promotes glycolysis, the pentose phosphate pathway, and nucleotide biosynthesis pathways [90]. Thus, DNA damage repair is enhanced, facilitating resistance to radiotherapy [91].
Genetic Analysis of Tyrosinemia Type 1 and Fructose-1, 6 Bisphosphatase Deficiency Affected in Pakistani Cohorts
Published in Fetal and Pediatric Pathology, 2020
Muhammad Yasir Zahoor, Huma Arshad Cheema, Sadaqat Ijaz, Zafar Fayyaz
Fructose 1,6 bisphosphatase deficiency (FBPD) is an autosomal recessive disorder caused by deficiency or absence of the fructose 1,6 bisphosphatase (FBPase) enzyme that converts fructose-1,6-bisphosphate (FBP) to fructose-6-phosphate (F-6-P) and inorganic phosphate, a critical step in gluconeogenesis. FBPase is encoded by the FBP1 gene, located at chromosome 9q22.3, which comprises eight exons and spans over 31 kb of DNA [7–9]. To date about 50 mutations causing FBPD have been reported in FBP1. Seventeen of these are missense mutations, one is a splicing defect, ten are small deletions, six are gross deletions, five are small insertions, and one is a small indel [10]. We have previously reported three mutations in FAH in three HT1 families [11] and three mutations of FBP1 in nine FBPD affected families [12]. We now report mutational analysis of FAH and FBP1 in four new tyrosinemia type 1 and eight new FBPD families, respectively.