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ADIPOSE TISSUE METABOLISM
Published in David M. Gibson, Robert A. Harris, Metabolic Regulation in Mammals, 2001
David M. Gibson, Robert A. Harris
Pyrophosphate (PP.) is hydrolvzcd further to 2P, by inorganic pyrophosphatase driving the reaction to completion. The acyl-CoA thiol esters are used hv acvl transferase enzymes to form ester linkages with glycerol 3-phosphate via its two hy droxy I groups. The product, phosphatide acid, is hydrolyzed bv a phosphatase to form diacvlglycerol (l)G). A third fattv acvl-CoA is then added bv an acvl transferase enzyme to form TG.
Affinity Modification — Organic Chemistry
Published in Dmitri G. Knorre, Valentin V. Vlassov, Affinity Modification of Biopolymers, 1989
Dmitri G. Knorre, Valentin V. Vlassov
An irreversible inhibition of nitrogenase (EC 1.18.2.1) observed in the presence of nitric oxide and nitrite can also be ascribed to the affinity modification process. This enzyme catalyzes the reduction of N2 to NH3 in the ATP-dependent reaction. It was proposed that the inactivating species is the NO molecule which imitates the enzyme substrate, binds to the protein, and disrupts in some way the essential for catalytic activity Fe4S4 cluster present in this enzyme.202 Sometimes a small ligand can be imitated by part of the structure of a larger molecule. Thus, inorganic phosphate was imitated by the affinity reagents methylphosphate and even 4-azido-2-nitrophenyl phosphate. The first reagent efficiently alkylated active-site carboxyl residues in inorganic pyrophosphatase (EC 3.6.1.1).203 The other reagent was used for photoaffinity modification of mitochondrial adenosine triphosphatase (EC 3.6.1.3) at the single inorganic phosphate binding site present in this enzyme.204 In more complex molecules this situation is routine and very often only part of the reagent structure is involved in recognition. Thus, in the affinity reagent p-iodoacetamidosalicylic acid XIX synthesized by Backer in the very beginning of the affinity modification studies, only a small part of the structure imitates lactate, the substrate of lactate dehydrogenase (see Section II.A).
The Modification of Arginine
Published in Roger L. Lundblad, Claudia M. Noyes, Chemical Reagents for Protein Modification, 1984
Roger L. Lundblad, Claudia M. Noyes
Studies from Cooperman’s laboratory48 on the modification of yeast inorganic pyrophosphatase presented some interesting data on the stability of the reaction product between arginine and phenylglyoxal. Figure 36 shows the change in the UV spectrum of the adduct between 2 molecules of phenylglyoxal and 1 molecule of arginine on incubation in 0.1 Msodium phosphate, pH 8.0. These data are consistent with a model for reaction where there is a rapid dissociation to form free arginine and reagent followed by the formation of a new reaction product with undefined stoichiometry. This study also provided an excellent example of the rigorous evalution of reaction stoichiometry as shown in Figure 37.
A study of Rose Bengal against a 2-keto-3-deoxy-d -manno-octulosonate cytidylyltransferase as an antibiotic candidate
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Suwon Kim, Seri Jo, Mi-Sun Kim, Dong Hae Shin
The screening of about two hundred chemical compounds (Supplementary Table 1) was performed with a malachite green assay method which is a photometric method31. The principle of this method is: when KdsBs transfer the cytidine 5′-monophosphate (CMP) moiety from cytidine 5′-triphosphate (CTP) to KDO, CMP-KDO, and pyrophosphate (PPi) are produced. PPi was decomposed into two phosphates by inorganic pyrophosphatase (IPP) and phosphates were measured by the malachite green method. CTP and KDO purchased from Sigma (St. Louis, MO) were used as a real substrate. A colour reagent of the malachite green method for phosphate detection was a mixture of ammonium molybdate ((NH4)6Mo7O24), malachite green solution and Tween 20 in the ratio 1:3:0.1. The mixture was filtered through a 0.20 μm PVDF syringe filter (Younginfrontier Inc., Seoul, Republic of Korea) and allowed to stand at room temperature (RT) for 1 h before use. The probability of inhibitory function of each chemical was investigated by detecting the difference in absorbance between the reaction mixtures with and without KdsBs.
A study of inhibitors of d -glycero-β-d -manno-heptose-1-phosphate adenylyltransferase from Burkholderia pseudomallei as a potential antibiotic target
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Suwon Kim, Seri Jo, Mi-Sun Kim, Dong Hae Shin
The screening of about 150 chemical compounds (Table S1) was performed with a malachite green assay method18. The principle of this method is: when SNTs transfer the AMP moiety from ATP to the heptose, ADP-d-glycero-β-d-manno-heptose and pyrophosphate (PPi) are produced. PPi was decayed into two phosphates by inorganic pyrophosphatase (IPP) and phosphates were measured by the malachite green method. β-d-Glucose-1-phosphate (βG1P) was purchased from Tokyo Chemical Industry Co. (Tokyo, Japan); TCI was used as a substrate because it is difficult to obtain the actual substrate, d-glycero-β-d-manno-heptose-1-phosphate (βH1P). The content of the α-form of this product was less than 0.1% in the current lot. A colour reagent of the malachite green method for phosphate detection was a mixture of ammonium molybdate ((NH4)6Mo7O24), malachite green solution and Tween 20 in the ratio 1:3:0.1. The mixture was filtered with a PVDF syringe filter and stood at room temperature (RT) for 1 h before use. All chemicals (25 μM) were tested for their inhibitory potential through a comparison of actual absorbances with control at 620 nm. The actual absorbance was obtained from the difference in absorbance between the reaction mixtures with and without BpHldC. The reaction mixture included 10 mM Tris–HCl (pH 7.5), 10 mM MgCl2, 0.04 unit IPP, and 0.025 mg ml−1BpHldC (1.3 µM). To evaluate the accuracy of the inhibitor screening, Z′ factor was determined to be 0.9 (n = 15). The results indicate that the accuracy of the enzyme inhibitor test using this method is excellent19.
Circ_0067934 reduces JNK phosphorylation through a microRNA-545-3p/PPA1 axis to enhance tumorigenesis and cisplatin resistance in ovarian cancer
Published in Immunopharmacology and Immunotoxicology, 2022
Yingchun Yin, Jing Li, Jiansheng Rong, Baohua Zhang, Xinmei Wang, Hongmei Han
At least 75% of the human genome is transcribed into RNAs which fulfill versatile functions in diverse cell types [8]. Emerging studies have suggested that some RNA transcripts, termed competitive endogenous RNAs (ceRNAs), sponge a microRNA (miRNA) and block its inhibitory effects on other protein-coding transcripts (mRNAs) [9,10]. Circular RNAs (circRNAs) are a class of ceRNAs that are abundantly expressed in mammalian transcriptome and are frequently involved in human diseases [11,12]. They are generally in loop structures originating from head-to-tail back-splicing of pre-mRNA where the 5′ and 3′ ends are covalently linked [13]. The involvements of circRNAs and their interaction with other transcripts have been increasingly reported in OC [14,15]. Circ_0067934 is generated from chromosomal region 3q26.2 by back splicing, which was initially confirmed as an oncogene in esophageal squamous cell carcinoma [16]. Likewise, circ_0067934 has been suggested to play oncogenic roles in other gynecologic malignancies such as cervical cancer [17] and breast cancer [18]. However, the role of circ_0067934 in OC remains to be defined. The bioinformatic analyses suggested miR-545-3p as a target of circ_0067934 and inorganic pyrophosphatase 1 (PPA1) mRNA as a target of miR-545-3p. miR-545-3p has been reported as a tumor-suppressor in hepatocellular carcinoma [19]. Intriguingly, downregulation of miR-545-3p has been suggested to be relevant to reduced cytotoxicity of DDP in lung cancer cells [20]. On the contrary, PPA1 has been demonstrated as a biomarker correlated with poor prognosis of OC patients [21]. Still, the functions of PPA1 in OC tumorigenesis and drug resistance are not completely clear yet. Taken together, we surmised that there is a circ_0067934/miR-545-3p/PPA1 axis in OC tumorigenesis.