scholarly journals A Dogma in Doubt: Hydrolysis of Equatorial Ligands of Pt IV Complexes under Physiological Conditions

2019 ◽  
Vol 58 (22) ◽  
pp. 7464-7469 ◽  
Author(s):  
Alexander Kastner ◽  
Isabella Poetsch ◽  
Josef Mayr ◽  
Jaroslav V. Burda ◽  
Alexander Roller ◽  
...  
Keyword(s):  
Physiological Conditions ◽  
Hydrolysis Of

Intestinal Absorption of Dipeptides Containing Glycine, Phenylalanine, Proline, β-Alanine or Histidine in the Rat

1973 ◽  
Vol 45 (6) ◽  
pp. 849-858 ◽  
Author(s):  
D. J. Boullin ◽  
R. F. Crampton ◽  
Christine E. Heading ◽  
D. Pelling
Keyword(s):  
Intestinal Absorption ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Peptide Absorption ◽  
Physiological Conditions ◽  
Anaesthetized Rats ◽  
Tissue Homogenates ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

1. The intestinal absorption of carnosine, glycylglycine, glycyl-d-phenylalanine, glycyl-l-phenylalanine, glycyl-l-proline and l-prolylglycine were investigated after intraluminal injection of dipeptide into anaesthetized rats. 2. With all six dipeptides, the intact substance was detected by ion-exchange chromatography in blood samples taken from the superior mesenteric vein. 3. The rate of hydrolysis of the dipeptides in tissue homogenates was measured in vitro. 4. The relative rates of hydrolysis varied by a factor of 300; there was an apparent inverse relationship between rate of hydrolysis and detection of intact peptide. 5. Peptide absorption was accompanied by increases in venous concentrations of the component amino acids, which appeared in proportions appropriate to the view that peptide absorption preceded hydrolysis. 6. It is suggested that slowly hydrolysed dipeptides may pass intact through the intestine wall under physiological conditions.

An active immunization approach to generate protective catalytic antibodies

2001 ◽  
Vol 360 (1) ◽  
pp. 151-157 ◽  
Author(s):  
Jun WANG ◽  
Yunqing HAN ◽  
Miles F. WILKINSON
Keyword(s):  
Active Immunization ◽  
Catalytic Antibodies ◽  
Toxic Substances ◽  
Mouse Blood ◽  
Physiological Conditions ◽  
Catalytic Function ◽  
Carbamate Insecticide ◽  
Hydrolysis Of

We report that mice immunized with a phosphate immunogen produced polyclonal catalytic antibodies (PCAbs) that catalysed the hydrolysis of carbaryl, a widely used broad-spectrum carbamate insecticide that exerts toxic effects in animals and humans. The reaction catalysed by the PCAbs (IgGs) obeyed Michaelis–Menten kinetics in vitro with the following values at pH8.0 and 25°C: Km≈ 8.0μM, kcat = 4.8×10−3–5.8×10−1, kcat/knon-cat = 5.6×101–6.8×103 (where knon-cat is the rate constant of the reaction in the absence of added catalyst). The PCAbs were also active in whole sera under physiological conditions in vitro. The PCAbs induced in vivo were also active in vivo, as immunization with the phosphate immunogen decreased the mouse blood concentration of carbaryl. To our knowledge, this is the first report demonstrating that active immunization generates antibodies possessing therapeutic catalytic function in vivo. We propose that active immunization schemes that induce enzymically active antibodies may provide a highly specific therapeutic approach for degrading toxic substances.

Refinement of the Kinetic Model of the 2-[14C]Deoxyglucose Method to Incorporate Effects of Intracellular Compartmentation in Brain

1989 ◽  
Vol 9 (3) ◽  
pp. 290-303 ◽  
Author(s):  
K. Schmidt ◽  
G. Lucignani ◽  
K. Mori ◽  
T. Jay ◽  
E. Palombo ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Rate Constant ◽  
Step Process ◽  
Precursor Pool ◽  
Physiological Conditions ◽  
Dg Method ◽  
Yield Values ◽  
Rate Limiting ◽  
Hydrolysis Of ◽  
Deoxyglucose Method

A translocase to transport hexose phosphate formed in the cytosol into the cisterns of the endoplasmic reticulum, where the phosphatase resides, is absent in brain (Fishman and Karnovsky, 1986). 2-Deoxyglucose-6-phosphate (DG-6-P) may therefore have limited access to glucose-6-phosphatase (G-6-Pase), and transport of the DG-6-P across the endoplasmic reticular membrane may be rate limiting to its dephosphorylation. To take this compartmentation into account, a five-rate constant (5K) model was developed to describe the kinetic behavior of 2-deoxyglucose (DG) and its phosphorylated product in brain. Loss of DG-6-P was modeled as a two-step process: (a) transfer of DG-6-P from the cytosol into the cisterns of the endoplasmic reticulum; (b) hydrolysis of DG-6-P by G-6-Pase and subsequent return of the free DG to the precursor pool. Local CMRglc (LCMRglc) was calculated in the rat on the basis of this model and compared with values calculated on the basis of the three-rate constant (3K) and the four–rate constant (4K) models of the DG method. The results show that under normal physiological conditions all three models yield values of LCMRglc that are essentially equivalent for experimental periods between 25 and 45 min. Therefore, the simplest model, the 3K model, is sufficient. For experimental periods from 60 to 120 min, the 4K and 5K models do not correct completely for loss of product, but the 5K model does yield estimates of LCMRglc that are closer to the values at 45 min than those obtained with the 3K and 4K models.

scholarly journals Selective inhibition of Zn2+-glycerophosphocholine cholinephosphodiesterase by tellurium tetrachloride

1992 ◽  
Vol 284 (3) ◽  
pp. 641-643 ◽  
Author(s):  
D E Sok ◽  
M R Kim
Keyword(s):  
Metal Ions ◽  
Mouse Brain ◽  
Selective Inhibition ◽  
Inhibitory Effect ◽  
Physiological Conditions ◽  
Neutral Ph ◽  
Tellurium Tetrachloride ◽  
Hydrolysis Of ◽  
Competitive Pattern

A Zn(2+)-glycerophosphocholine cholinephosphodiesterase (EC 3.1.4.38) purified from mouse brain was found to be reversibly inhibited by tellurium tetrachloride. This effect was characterized by a competitive pattern of inhibition, with apparent Ki values of 0.7 microM and 1.5 microM for the hydrolysis of p-nitrophenylphosphocholine and glycerophosphocholine respectively. Interestingly, the inhibitory effect of tellurium tetrachloride was found to be greatly potentiated by tetramethylammonium salt, indicative of a synergistic interaction between the two compounds. Additionally, it was observed that the effect of tellurium tetrachloride was not affected by a number of other metal ions, and was more pronounced at neutral pH, suggesting that the inhibitory role of the tellurium tetrachloride may be of importance under physiological conditions. Thus Zn(2+)-glycerophosphocholine cholinephosphodiesterase is proposed to be one of the target enzymes which is susceptible to the inhibitory effect of tellurium tetrachloride.

Role of Metal Ion in Specific Recognition of Pyrophosphate Ion under Physiological Conditions and Hydrolysis of the Phosphoester Linkage by Alkaline Phosphatase

2013 ◽  
Vol 52 (19) ◽  
pp. 11034-11041 ◽  
Author(s):  
Priyadip Das ◽  
Nellore Bhanu Chandar ◽  
Shishir Chourey ◽  
Hridesh Agarwalla ◽  
Bishwajit Ganguly ◽  
...  
Keyword(s):  
Alkaline Phosphatase ◽  
Metal Ion ◽  
Physiological Conditions ◽  
Specific Recognition ◽  
Hydrolysis Of

scholarly journals The speed of partial reactions of the uncoating ATPase Hsc70 depends on the source of coated vesicles

1996 ◽  
Vol 109 (3) ◽  
pp. 705-711
Author(s):  
E. Buxbaum ◽  
P.G. Woodman
Keyword(s):  
Bovine Brain ◽  
Coated Vesicles ◽  
Physiological Conditions ◽  
Atp Turnover ◽  
Hydrolysis Of

Hsc70 was previously isolated by its ability to catalyse the uncoating of clathrin-coated vesicles from bovine brain. We have recently shown that Hsc70 is more active towards coated vesicles from brain than those from other tissues. In order to gain information on the mechanistic reason for this difference we have examined the ability of brain and placental coated vesicles to stimulate partial reactions during a single round of ATP turnover. The Hsc70-ATP complex is turned over to Hsc70-ADP center dot Pi, from which phosphate is slowly released. The resulting Hsc70-ADP complex exchanges ATP for ADP. Dissociation of ATP or ADP from Hsc70 does not seem to occur under physiological conditions. The hydrolysis of ATP is accelerated by the presence of clathrin-coated vesicles, with vesicles from brain being about twice as effective as vesicles from placenta. Additionally, it appears that brain, but not placental, coated vesicles can also stimulate the exchange of ADP for ATP.

Sign in / Sign up

Export Citation Format

Share Document