scholarly journals The Role of Magnesium, Pyrophosphate, and Their Complexes as Substrates and Activators of the Vacuolar H+-Pumping Inorganic Pyrophosphatase (Studies Using Ligand Protection from Covalent Inhibitors)

1996 ◽  
Vol 111 (1) ◽  
pp. 195-202 ◽  
Author(s):  
R. Gordon-Weeks ◽  
S. H. Steele ◽  
R. A. Leigh
Keyword(s):  
Inorganic Pyrophosphatase ◽  
Magnesium Pyrophosphate ◽  
Covalent Inhibitors

scholarly journals The role of histidine-118 of inorganic pyrophosphatase from thermophilic bacterium PS-3

1991 ◽  
Vol 278 (2) ◽  
pp. 595-599 ◽  
Author(s):  
N Hirano ◽  
T Ichiba ◽  
A Hachimori
Keyword(s):  
Thermophilic Bacterium ◽  
Complete Loss ◽  
Inorganic Pyrophosphatase ◽  
Histidine Residue ◽  
First Order ◽  
Diethyl Pyrocarbonate ◽  
Lysyl Endopeptidase ◽  
First Order Kinetics ◽  
Pseudo First Order

Treatment of the inorganic pyrophosphatase from thermophilic bacterium PS-3 with diethyl pyrocarbonate resulted in the almost complete loss of its activity, which followed pseudo-first-order kinetics. The presence of Mg2+ prevented the inactivation. Enzyme inactivated with diethyl pyrocarbonate was re-activated by hydroxylamine. The inactivation parallelled the amount of modified histidine residue, and a plot of the activity remaining against the amount of modified histidine residue suggested that the modification of one of two histidine residues totally inactivated the enzyme. The site involved was found to be located in a single lysyl endopeptidase-digest peptide derived from the ethoxy[14C]carbonylated enzyme. Amino acid analysis and sequence analysis of the peptide revealed that it comprised residues 96-119 of the inorganic pyrophosphatase from thermophilic bacterium PS-3. These results, when compared with those reported for the Escherichia coli and yeast enzymes, imply that His-118 of the inorganic pyrophosphatase from thermophilic bacterium PS-3 is located near the Mg(2+)-binding site and thus affects the binding of Mg2+.

scholarly journals Role of Vacuolar H+-inorganic Pyrophosphatase in Tomato Fruit Development

2012 ◽  
Vol 63 (15) ◽  
pp. 5613-5621 ◽  
Author(s):  
S. A. Mohammed ◽  
S. Nishio ◽  
H. Takahashi ◽  
K. Shiratake ◽  
H. Ikeda ◽  
...  
Keyword(s):  
Fruit Development ◽  
Tomato Fruit ◽  
Inorganic Pyrophosphatase

scholarly journals Targeting KRAS in Lung Cancer Beyond KRAS G12C Inhibitors: The Immune Regulatory Role of KRAS and Novel Therapeutic Strategies

2022 ◽  
Vol 11 ◽  
Author(s):  
Marc Cucurull ◽  
Lucia Notario ◽  
Montse Sanchez-Cespedes ◽  
Cinta Hierro ◽  
Anna Estival ◽  
...  
Keyword(s):  
Tumor Heterogeneity ◽  
Regulatory Role ◽  
Lung Cancers ◽  
Downstream Signaling ◽  
Tumor Immune Microenvironment ◽  
Covalent Inhibitors ◽  
Early Phase Clinical Trials ◽  
Novel Therapeutic Strategies ◽  
Lung Adenocarcinomas

Approximately 20% of lung adenocarcinomas harbor KRAS mutations, an oncogene that drives tumorigenesis and has the ability to alter the immune system and the tumor immune microenvironment. While KRAS was considered “undruggable” for decades, specific KRAS G12C covalent inhibitors have recently emerged, although their promising results are limited to a subset of patients. Several other drugs targeting KRAS activation and downstream signaling pathways are currently under investigation in early-phase clinical trials. In addition, KRAS mutations can co-exist with other mutations in significant genes in cancer (e.g., STK11 and KEAP1) which induces tumor heterogeneity and promotes different responses to therapies. This review describes the molecular characterization of KRAS mutant lung cancers from a biologic perspective to its clinical implications. We aim to summarize the tumor heterogeneity of KRAS mutant lung cancers and its immune-regulatory role, to report the efficacy achieved with current immunotherapies, and to overview the therapeutic approaches targeting KRAS mutations besides KRAS G12C inhibitors.

ATP as effector of inorganic pyrophosphatase of Escherichia coli. The role of residue Lys112 in binding effectors

2007 ◽  
Vol 72 (1) ◽  
pp. 100-108 ◽  
Author(s):  
E. V. Rodina ◽  
N. N. Vorobyeva ◽  
S. A. Kurilova ◽  
T. S. Sitnik ◽  
T. I. Nazarova
Keyword(s):  
Escherichia Coli ◽  
Inorganic Pyrophosphatase

scholarly journals The ‘aromatic patch’ of three proximal residues in the human acetylcholinesterase active centre allows for versatile interaction modes with inhibitors

1998 ◽  
Vol 335 (1) ◽  
pp. 95-102 ◽  
Author(s):  
Naomi ARIEL ◽  
Arie ORDENTLICH ◽  
Dov BARAK ◽  
Tamar BINO ◽  
Baruch VELAN ◽  
...  
Keyword(s):  
Structural Diversity ◽  
Huperzine A ◽  
Anionic Site ◽  
Active Centre ◽  
Aromatic Residues ◽  
X Ray ◽  
Structural Differences ◽  
Covalent Inhibitors ◽  
Modes Of Interaction

The role of the functional architecture of the human acetylcholinesterase (HuAChE) active centre in accommodating the non-covalent inhibitors tacrine and huperzine A, or the carbamates pyridostigmine and physostigmine, was analysed using 16 mutants of residues lining the active-centre gorge. Despite the structural diversity of the ligands, certain common properties of the complexes could be observed: (a) replacement of aromatic residues Tyr133, Tyr337 and especially Trp86, resulted in pronounced changes in stability of all the complexes examined; (b) effects due to replacements of the five other aromatic residues along the active-centre gorge, such as the acyl pocket (Phe295, Phe297) or at the peripheral anionic site (Tyr124, Trp286, Tyr341) were relatively small; (c) effects due to substitution of the carboxylic residues in the gorge (Glu202, Glu450) were moderate. These results and molecular modelling indicate that the aromatic side chains of residues Trp86, Tyr133 and Tyr337 form together a continuous ‘aromatic patch ’ lining the wall of the active-centre gorge, allowing for the accommodation of the different ligands via multiple modes of interaction. Studies with HuAChE mutants carrying replacements at positions 86, 133 and 337 indicate that the orientations of huperzine A and tacrine in the HuAChE complexes in solution are significantly different from those observed in X-ray structures of the corresponding complexes with Torpedo californica AChE (TcAChE). These discrepancies may be explained in terms of structural differences between the complexes of HuAChE and TcAChE or, more likely, by the enhanced flexibility of the AChE active-centre gorge in solution as compared with the crystalline state.

scholarly journals A STUDY OF THE NUCLEOSIDE TRI- AND DIPHOSPHATE ACTIVITIES OF RAT LIVER MICROSOMES

1962 ◽  
Vol 15 (3) ◽  
pp. 563-578 ◽  
Author(s):  
Lars Ernster ◽  
Lois C. Jones
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Physiological Role ◽  
Sodium Deoxycholate ◽  
Inorganic Pyrophosphatase ◽  
Rat Liver Microsomes ◽  
High Concentrations ◽  
Hydrolysis Of ◽  
No Activation

Rat liver microsomes catalyze the hydrolysis of the triphosphates of adenosine, guanosine, uridine, cytidine, and inosine into the corresponding diphosphates and inorganic orthophosphate. The activities are stimulated by Na2S2O4, and inhibited by atebrin, chlorpromazine, sodium azide, and deaminothyroxine. Sodium deoxycholate inhibits the ATPase activity in a progressive manner; the release of orthophosphate from GTP and UTP is stimulated by low, and inhibited by high, concentrations of deoxycholate, and that from CTP and ITP is unaffected by low, and inhibited by high, concentrations of deoxycholate. Subfractionation of microsomes with deoxycholate into ribosomal, membrane, and soluble fractions reveals a concentration of the triphosphatase activity in the membrane fraction. Rat liver microsomes also catalyze the hydrolysis of the diphosphates of the above nucleosides into the corresponding monophosphates and inorganic orthophosphate. Deoxycholate strongly enhances the GDPase, UDPase, and IDPase activities while causing no activation or even inhibition of the ADPase and CDPase activities. The diphosphatase is unaffected by Na2S2O4 and is inhibited by azide and deaminothyroxine but not by atebrin or chlorpromazine. Upon fractionation of the microsomes with deoxycholate, a large part of the GDPase, UDPase, and IDPase activities is recovered in the soluble fraction. Mechanical disruption of the microsomes with an Ultra Turrax Blender both activates and releases the GDPase, UDPase, and IDPase activities, and the former effect occurs more readily than the latter. The GDPase, UDPase, and IDPase activities of the rat liver cell reside almost exclusively in the microsomal fraction, as revealed by comparative assays of the mitochondrial, microsomal, and final supernatant fractions of the homogenate. The microsomes exhibit relatively low nucleoside monophosphatase and inorganic pyrophosphatase activities, and these are unaffected by deoxycholate or mechanical treatment. Different approaches toward the function of the liver microsomal nucleoside tri- and diphosphatases are reported, and the possible physiological role of the two enzymes is discussed.

Inorganic pyrophosphatase activity in oral streptococci: purification and properties of the enzyme from Streptococcus salivarius

1982 ◽  
Vol 60 (4) ◽  
pp. 452-462 ◽  
Author(s):  
Ramji L. Khandelwal ◽  
Ian R. Hamilton
Keyword(s):  
Enzyme Activity ◽  
Deae Cellulose ◽  
Inorganic Pyrophosphatase ◽  
Phosphate Ester ◽  
Oral Streptococci ◽  
Streptococcus Salivarius ◽  
Inorganic Pyrophosphate ◽  
Magnesium Pyrophosphate ◽  
Pyrophosphatase Activity ◽  
Hydrolysis Of

Inorganic pyrophosphatase has been purified from the soluble fraction of Streptococcus salivarius by protamine sulfate treatment, ammonium sulfate fractionation, and chromatography on Sephadex G-200 and DEAE-cellulose. The enzyme was purified approximately 500-fold with a 33% yield. The purified enzyme was homogeneous since it showed a single band when examined by nondenaturing polyacrylamide gel electrophoresis. It was rich in acidic (glutamic and aspartic) amino acids, as well as serine and glycine. The enzyme was devoid of sulfur-containing amino acids.The purified enzyme was specific for the hydrolysis of inorganic pyrophosphate and did not hydrolyze any other phosphate-ester compound examined. Inorganic pyrophosphatase activity was completely dependent on a divalent cation. Activity was maximum in the presence of Mg2+ while activity in the presence of Mn2+ and Co2+ was significantly lower. In the presence of Mg2+, a number of divalent cations, however, inhibited the enzyme activity. The true substrates for S. salivarius inorganic pyrophosphatase were magnesium–pyrophosphate complexes, i.e., MgPPi and Mg2PPi, while free Mg2+ had no effect on the enzyme activity and free PPi inhibited the hydrolysis of inorganic pyrophosphate. Km value for magnesium–pyrophosphate complexes was 16.4 μM. Km value for total Mg2+ was similar ranging between 14.4 and 20 μM. Analysis of data by Hill plots indicated one binding site for Mg2+ and two for PPi. Among various nucleotides and glycolytic intermediates examined, GDP, GMP, and fructose-1,6-P2 showed significant inhibitory effect on enzyme activity.

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