Homology of lysozymes of bacterial and vertebrate origin

Theoretical analysis of structural and functional organization of vertebrate lysozymes, T4-phage lysozyme, lambda-phage endolysin and extracellular lysozyme of Chalaropsis species suggests a genetic relationship between the enzymes in question. It has been shown that the lysozyme sequences exhibit both inter- and intramolecular homology. The obtained data lend support to the concept postulating a common ancestor for the lysozyme family and subsequent divergent evolution of these proteins. The two-component primary structure of lysozymes can result from structural gene duplication and allows to explain similar catalytic activity and different substrate specificity of these enzymes by the differentiation and specialization of functions of the N- and C-components of the protein chains.     

Calcium-binding lysozymes

It was found that pigeon lysozyme binds one calcium ion, as does equine lysozyme. The protein was eluted with equimolar calcium ions from a Bio-Gel P-60 column. The binding constants of equine and pigeon lysozymes were determined to be 2 x 10(6) and 1.6 x 10(7) M-1, respectively, in 0.1 M KCl at pH 7.1 and 20 degrees C. During evolution the gene of calcium-binding lysozyme is deduced to be separated from that of non-calcium-binding lysozyme by gene duplication before splitting of avian and mammalian lineages, from their amino-acid sequences. It is assumed that the alpha-lactalbumin might have evolved from calcium-binding lysozyme.     

Comparative effect of thiopental sodium on cortical evoked potentials of different origin

The minimal doses of thiopental sodium (TS) to suppress each of seven varieties of cortical evoked potentials tested were determined in experiments on cats. The preparation had the strongest effect on the following responses: interzonal, arising in the motor cortex to stimulation of somatosensory area I; the reflex pyramidal and late components of the direct pyramidal response. The oligosynaptic transcallosal potential is less sensitive than the above responses but more so than the callosal response. The action of TS on the response depends on the complexity of its organization. The level at which the given cortical response takes place must also be considered. Comparison of the action of TS on the I₁ wave of the pyramidal response and on the dendritic component of the direct cortical response showed that, given equal complexity of its organization, the response arising in deep layers of the cortex is depressed more by TS than the response arising wholly at the level of surface layer I.Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 264–271, May–June, 1972.     

Comparative immunochemical characteristics of different phosphodiesterases of cyclic nucleotides

Precipitating monospecific antibodies against purified bovine retinal rod outer segment phosphodiesterase (EC 3.1.4.17) were obtained from rabbit blood serum. These antibodies do not form precipitating complexes with phosphodiesterase isolated from rat or ox brain tissues or from the heart, lung, liver, kidney, testes and uterus of the rat. The antibodies inhibit the activity of retinal rod outer segment phosphodiesterase or that of rat brain, liver, heart and uterus enzyme (despite the lack of precipitation) but have no effect on the phosphodiesterase activity of preparations obtained from rat lungs, kidney or testes. The same effect on the phosphodiesterase activity of all these tissues is exerted by monovalent fragments of the antibodies. Using partially purified preparations of phosphodiesterase from retinal rod outer segments and brain of the ox and from human myometrium, the mechanisms of inhibition of the enzyme catalytic activity by the antibodies was studied. In the presence of the antibodies, the Km and V values appeared to be different, depending on the preparation. It was assumed that a certain site in the phosphodiesterase molecule is characterized by great structural rigidity. Taking into account the shifts in the Km values induced by the antibodies, the differences in the localization of the antigenic determinant in relation to the enzyme active center are discussed.     

Comparative analysis of sensitivity of cholinesterases of different origin to bis-onium reversible inhibitors

Analytical review of the literature data on interaction constant of cholinesterases from different animal (vertebrates and squids) with 45 bis-onium reversible inhibitors forming homologous series with regularly varied structure has been carried out. Values of the competitive, uncompetitive and generalized inhibitor constants are compared. Interspecies and intraspecies differences in sensitivity of ChE are revealed. Results of conformational analysis of the investigated ligand molecules are presented. The data on population of individual conformations are compared with the data on anticholinesterase potency. Conclusions are made on the action mechanism of the investigated compounds and predominant place of their sorption. The presented data are considered from the point of view of comparative biochemistry and in the light of current information about the active center structure of cholinesterases.     

Comparative analysis of sensitivity of cholinesterases of different origin to reversible bis-onium inhibitors

Analytical review of literature data has been carried out about kinetic parameters of cholinesterases (ChE) of various animals (vertebrates and squids) with 45 reversible bis-onium inhibitors forming homologous series with regularly changing structure. Values of competitive, non-competitive, and generalized inhibitory constants are compared. Interspecies and intraspecies differences are revealed in sensitivity of ChE to bis-onium inhibitors. Results of conformational analysis of molecules of the studied ligands are presented. Data on population of individual conformations are compared with values of anticholinesterase efficiency. Conclusions are made about mechanisms of action of the studied compounds and the predominant site of their sorption. The presented data are discussed from the point of view of comparative enzymology and in the light of the current information about structure of active center of cholinesterases.     

Comparative analysis of sensitivity of cholinesterases of different origin to monoonium reversible inhibitors

The analytic review of the literature data on constants of interaction of cholinesterases of different animal (vertebrates and squids) with 89 onium (ammonium, phosphonium, sulfonium) reversible inhibitors constituting homologous series with regularly varied structure is carried out. Values of the competitive, uncompetitive and generalized inhibitor constants are compared. On the basis of that, conclusions about the mechanism of action of the studied compounds and primary place of their sorption—in “anionic” or peripheral “anionic” sites of enzymes—are made. The presented data are considered from the point of view of comparative biochemistry and in light of current concepts of cholinesterase active center structure.     

Echinococcus granulosus of equine origin from different countries possess uniform morphological characteristics

Echinococcus granulosus of equine origin from different countries possess uniform morphological characteristics. International Journal for Parasitology16: 529–540. Detailed comparative studies on isolates of larval and adult Echinococcus granulosus of equine origin from England, Scotland, Ireland, Belgium, Switzerland, South Africa and New Zealand demonstrated the morphological uniformity of the equine parasite. The morphological features of the equine strain of E. granulosus were fully characterized and it was found that on the basis of morphology alone, this strain could be differentiated from all other inter- and intraspecific variants of Echinococcus that have been described. The most important differential morphological characters are the dimensions of both larval and adult rostellar hooks, shape of ovary, testes distribution and details of the cirrus. As a result of the present study, it is apparent that the equine strain of E. granulosus has a widespread geographical distribution and there is evidence that the parasite may extend its range in the future. The question of whether consideration should be given to recognizing the equine strain as a formal taxonomic entity is discussed.     

Comparative study of enzymatic activity of cholinesterases of different origin in thionaphthylacetate hydrolysis reactions

A comparative determination of kinetic parameters V and Km in the reaction of hydrolysis thionaphthylacetate and well known substrate acetylthiocholine by choline esterases from different sources was conducted. It is shown that butyrylcholine esterases hydrolyze thionaphthylacetate with velocity comparable with that of hydrolysis of acetylthiocholine, while acetylcholine esterases and propionylcholine esterases hydrolyze this substrate several times slower than acetylthiocholine. The values of Km in the reactions of hydrolysis of thionaphthylacetate for all studied cholinesterases is an order higher than for acetylthiocholine except cholinesterase of blood serum of fish. This value for the latter enzyme is practically equal.