Ligand binding and detoxication

In an organism the binding of a toxic chemical to a binding site can act as a detoxication mechanism when toxicity is a property of the unbound ligand. This qualitative statement has been evaluated in quantitative terms. To this end parameters have been defined for which numerical values are required, equations are derived and a procedure is outlined that allows assessment of when and to what extent binding is of value in detoxication. In the process two new quantities are introduced, i.e. the binding capacity and the binding activity, which make for easier handling and comparison of binding data. It is concluded that to be important in detoxication the numerical value of the binding activity must be greater than unity and the total ligand concentration should not exceed the binding capacity. These general conclusions can be further refined depending on the accuracy with which the values of the parameters involved are known. Due to its generality the results of the analysis are useful in all situations where it is desirable to know the magnitude of the free fraction of a bound chemical.     

Oxidative detoxication of thallium in the yeast mitochondria

When yeast cells are grown in thallium-containing broth, the thallium ion is oxidized in the mitochondria to Tl₂O₃. This oxide is subsequently discharged from the mitochondria and finally excreted from the protoplast.     

Enzyme systems of insecticide detoxication in the Colorado beetle

The activity of three enzymatic systems of xenobiotic metabolism (cytochrome P-450-dependent monooxygenases, non-specific esterases and glutathione S-transferases) was studied at different stages of development of the Colorado potato beetle (Leptinotarsa decemlineata). Significant sex and ontogenetic differences in the content of cytochrome P-450, position of maxima of CO-difference spectra of the cytochrome P-450 reduced form and substrate specificity of cytochrome P-450 were revealed. The activity of non-specific esterases was shown to increase depending on the age of larvae. The insecticide 1-naphtholenol methylcarbamate which is metabolized by the system of cytochrome P-450-dependent monooxygenases is more toxic in the larvae than at the imago stage, which is correlated with the activity of this system at different stages of ontogenesis. The microsomal monooxygenase inhibitor, piperonylbutoxide, increases the insecticide toxicity in the Colorado beetle imago more than 2-fold. The experimental results testify to different contribution of the detoxication systems to the sensitivity of the Colorado beetle to insecticides at various metamorphosis stages.     

Comparative detoxication. The detoxication of aromatic acids by invertebrates: detection of agmatine conjugates in scorpions

1. Benzoic acid and p-nitrobenzoic acid were converted in the scorpion Palamnaeus into N(1)-benzoylagmatine and N(1)-p-nitrobenzoylagmatine. 2. Some benzoyl- and p-nitrobenzoyl-arginine were also formed and these compounds were probable precursors of the agmatine derivatives. 3. p-Nitrobenzoyl- and p-aminobenzoyl-arginine were formed in millipedes dosed with the aromatic acids. 4. Woodlice excreted p-amino- and p-nitro-benzoic acid as their glycine conjugates and no conjugation could be found in the crab Gecarcinus and a freshwater crayfish Astacus.     

Status of the detoxication function of the liver after vagal denervation

In 14 and 25 days of bilateral subdiaphragmatic+ vagotomy perimeter of the endoplasmic reticulum (EPR) of hepatocytes, content of the enzyme (cytochrome R-450) built into the membrane in microsomal fractions, speed of hydroxylation of substrates and oxygen absorption decreased and the section area of EPR and duration of the hexonal sleep increased. The results demonstrate certain disturbances of the detoxication function of the denervated liver.     

A possible involvement of glutathione in the detoxication of sulfite

Inorganic sulfite may be detoxified by conversion to S-sulfocysteine. We demonstrate this conversion by a series of enzyme-catalyzed steps as follows. Inorganic sulfite reacts with glutathione disulfide by a thiol transferase catalyzed reaction as previously demonstrated. The S-sulfoglutathione formed is then converted by gamma-glutamyltranspeptidase to S-sulfocysteinylglycine and the latter finally hydrolyzed to S-sulfocysteine by a renal dipeptidase. S-Sulfoglutathione is a substrate for gamma-glutamyl-transpeptidase as effective as glutathione itself. Furthermore, S-sulfocysteinylglycine is cleaved as efficiently as cysteinylglycine by a renal dipeptidase at high substrate concentrations but somewhat less efficiently at low substrate concentrations.     

精制白喉毒素脱毒工艺的改进

为了改进精制白喉毒素脱毒工艺中存在的时间长和损失大等问题,我们考虑进行脱毒过程中加入Ｌ－赖氨酸协同脱毒的试验,并以原工艺进行比较,结果使原工艺存在的问题均得到较好的解决。