Fish Allergy
Andreas L. Lopata in Food Allergy, 2017
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.
Anaerobic endurance: the speed endurance sports
Nick Draper, Helen Marshall in Exercise Physiology, 2014
At the fourth step of glycolysis the enzyme aldolase catalyses the splitting of fructose-1,6-bisphosphate (a hexose, 6 carbon ring) into two triose (three carbon chain) molecules, dihydroxyacetone phosphate and glyceraldehyde-3-phosphate (G3P), each of which contains one of the phosphate groups. Catalysed by triose phosphate isomerase, dihydroxyacetone phosphate is then restructured in the fifth step of glycolysis to form another glyceraldehyde-3-phosphate. This reaction is necessary because only glyceraldehyde-3-phosphate can participate in the subsequent reactions of glycolysis. At this point the newly created glyceraldehyde-3-phosphate molecule can pass, along with the original glyceraldehyde-3-phosphate molecule, to the sixth step of glycolysis. From this point on, therefore, there are two molecules of each metabolite, derived from the original single glucose molecule.
Affinity Modification — Organic Chemistry
Dmitri G. Knorre, Valentin V. Vlassov in Affinity Modification of Biopolymers, 1989
A special type of modification of enzymes is paracatalytic modification. This type of modification is based on the ability of enzymes to convert substrates to intermediate species capable of reacting with extrinsic chemical reagents which normally do not touch the substrates. In some cases, these by-reactions of enzymatic processes lead to the formation of reactive compounds which modify the enzymes covalently and cause inactivation. The most thoroughly investigated paracatalytic reactions are those for the enzymes forming readily oxidizable carbanion intermediates.173 The typical example is fructose 1,6-bis-phosphate aldolase, an intermediate enzyme of glycolysis (Chapter 1, Figure 9) catalyzing the reversible cleavage of fructose-1,6-bis-phosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate (DHP). In the course of catalysis the enzyme forms a carbanion, the resonanse structure of enamine intermediate Schiff base formed by DHP and the E-NH2 group of lysine residue in the active center.
Interaction of low frequency external electric fields and pancreatic β-cell: a mathematical modeling approach to identify the influence of excitation parameters
Published in International Journal of Radiation Biology, 2018
Sajjad Farashi, Pezhman Sasanpour, Hashem Rafii-Tabar
The glycolysis pathway contains a series of reactions for converting glucose into pyruvate and ATP. In the first step glucose is phosphorylated and converted to glucose-6-phosphate (G6P) which will be isomerised to the fructose-6-phosphate (F6P). The further phosphorylation of F6P by phosphofructokinase-1 enzyme produces fructose 1,6-bisphosphate, which in the next step will be cleaved into glyceraldehyde-3-phosphate (G3P) and dihydroxy acetone phosphate (DHAP) using aldolase enzyme. The DHAP is converted to further G3P by triose-phosphate isomerase. This phase, the procedure is preparatory phase and requires energy consumption. In the next step G3P oxidized to 1,3-bisphosphoglycerate incorporating glyceraldehyde 3-phosphate dehydrogenase. A large amount of energy during the oxidation of an aldehyde group will be released. In this step Nicotinamide adenine dinucleotide (NAD+) will be reduced to NADH, the reduced form of NAD+. The enzyme phosphoglycerate kinase transfers the phosphoryl group of 1,3-bisphosphoglycerate to ADP and producing ATP and 3-phosphoglycerate which the latter will be isomerized to 2-phosphoglycerate using Phosphoglycerate mutase. Using the enzyme enolase, 2-phosphoglycerate will be converted to phosphoenolpyruvate (PEP). Finally, PEP will be converted to pyruvate by pyruvate kinase. In this step one extra ATP molecule will be produced. The glycolysis pathway is depicted in Figure 1.
Prostate cancer proteomics: clinically useful protein biomarkers and future perspectives
Published in Expert Review of Proteomics, 2018
Paula Intasqui, Ricardo P. Bertolla, Marcus Vinicius Sadi
To explore cell resistance to chemotherapy treatment with docetaxel, the phosphoproteomes of sensitive (DU145 and PC3) and resistant (DU145-Rx and PC3-Rx) cells were compared, and 365 tyrosine phosphorylation sites of 215 proteins were altered. In the docetaxel-resistant cells, phosphorylation of proteins involved with focal adhesions and the cytoskeleton, such as ACTN1, alpha-actinin-4 (ACTN4), focal adhesion kinase 1 (PTK2), VIM, CAV1, and annexin A1 (ANXA1) was observed. Interestingly, by inhibiting PTK2 phosphorylation during docetaxel treatment, chemoresistance was reversed, decreasing cell viability through an increase in cell autophagy, rather than apoptosis [42]. Radioresistance was also studied by comparing the proteome of CaP radiation-sensitive and resistant cells. PI3K/Akt/mTOR, VEGF, and glucose metabolism were the major altered pathways, demonstrating that these may play important roles in the radioresistance. Fructose-bisphosphate aldolase A (ALDOA), involved with glycolysis, was increased in all analyzed CaP-resistant cell lines. The association between ALDOA expression and radioresistance was validated by western blotting, immunohistochemistry, animal xenografts, and knockdown models, which demonstrated that suppression of ALDOA increases radiosensitivity [43].
Inhibitors of glucosamine-6-phosphate synthase as potential antimicrobials or antidiabetics – synthesis and properties
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Joanna Stefaniak, Michał G. Nowak, Marek Wojciechowski, Sławomir Milewski, Andrzej S. Skwarecki
Leriche et al.64 studied the Fru-6-P binding site at the ISOM domain of E. coli GlcN-6-P synthase, using anhydro-1,2-hexitol-6-phosphate 40 (Scheme 9C), a structural analogue of an open ring form of Fru-6-P, which was previously identified as an irreversible inhibitor of phosphoglucose isomerase. To obtain 40, the authors used racemic glycidol 41 as a starting material, which was oxidised to a corresponding aldehyde 42via the Moffat oxidation. The formed aldehyde was then chemoenzymatically condensed with glycerone phosphate, using aldolase. The resulting intermediate was then reduced using sodium borohydride which led to the racemic 40. This compound inactivated GlcN-6-P synthase, with Ki = 1.4 mM64.
Related Knowledge Centers
- Calvin Cycle
- Enzyme
- Gluconeogenesis
- Reversible Reaction
- Aldol
- Fructose 1,6-Bisphosphate
- Dihydroxyacetone Phosphate
- Glyceraldehyde 3-Phosphate
- Fructose 1-Phosphate
- Sedoheptulose-Bisphosphatase