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Biomedical subjects

M Sokolovsky

Publications and source records attributed to M Sokolovsky.

At least 199 records · Page 11Linked to original sources
PubMed1976

Purification and crystallization of human carboxypeptidase A.

Human carboxypeptidase A has been isolated from activated pancreatic juice by means of affinity chromatography employing the competitive inhibitor benzylsuccinic acid as an affinity ligand. The structural and functional features of the human and bovine enzymes are quite analogous. The molecular weights of human and bovine carboxypeptidases A are virtually identical, their amino acid compositions are similar, both contain 1 g-atom of zinc/mole, and the activities of both are restored by addition of zinc to the apoenzyme. The inhibition of human carboxypeptidase by chelating agent is reversed by either dilution or addition of a metal such as Cu2+. When other metals are substituted for the native zinc, peptidase activity of the human metallocarboxypeptidases follows the order: cobalt greater than nickel greater than manganese greater than cadmium, while the sequence for esterase activities is: manganese greater than cobalt = cadmium greater than nickel. The latter sequence differs from that observed for the bovine enzyme. Human carboxypeptidase A crystallizes after dialysis at low ionic strength. Hydrolysis of the dipeptide carbobenzoxyglycyl-L-phenylalanine and of the ester benzoylglycyl-L-alpha-hydroxy-beta-phenyllactate exhibits kinetic anomalies, but that of their longer homologues does not. Chemical modifications with tyrosine reagents alters esterase and peptidase activities. The affinity chromatographic method here described should greatly facilitate future studies of this enzyme from human and other sources.

Amino Acids↗
PubMed1975

Nuclear-magnetic-resonance studies of carboxypeptidase B. Binding of inhibitors to the manganese enzyme.

Longitudinal and transverse proton relaxation rates of water in solutions of porcine manganese carboxypeptidase B have been measured in the presence of various competitive inhibitors by pulse nuclear magnetic resonance (NMR) spectrometry. The inhibition constant of Mn-carboxypeptidase activity by L-argininic acid and acetyl-L-arginine was in agreement with the equilibrium constant obtained by the NMR method, indicating similar and specific binding of the inhibitors to the active site of the manganese enzyme. Titration of the water boound to the metal ion revealed the presence of one water molecular which could be displaced from the sphere of the managenese ion by various inhibitors. The structural features of the inhibitors required for this displacement as well as the mode of interaction is described.

Animals↗
PubMed1975

Photoreactions of phosphorothioate and cysteamine-S-phosphate. Photosubstitution and photophosphoryl transfer.

The photoreactions of phosphorothioate and cysteamine-S-phosphate were investigated. On irradiation of phosphorothioate a marked change in absorption spectrum was observed. The product migrated in high voltage electrophoresis, with different mobility from that of phosphorothioate and its dimer, or inorganic orthophosphate. It contained phosphate and sulfur in a ratio of 2: 1, without reducing properties. Therefore it was suggested that the product is either pyrothiophosphate, or a cyclic compound, with similar composition. On irradiation of phosphorothioate in the presence of potential phosphoryl group acceptor, such as glucose or galactose, 25-40% of the phosphoryl group was transferred. The formation of glucose 6-phosphate, or galactose 6-phosphate was observed. The photolysis of cysteamine-S-phosphate gave cysteamine, inorganic orthophospate and taurine. Under the same conditions of irradiation, inorganic orthophosphate or aminoethanol-O-phosphate were found to be stable.

Cysteamine↗
PubMed1975

On the interaction of esters and peptides with carboxypeptidase B.

The specificity of porcine carboxypeptidase B towards basic and non-basic substrates was studied by employing several esters of phenyllactate. The structure of these depsipeptides complement exactly those of the corresponding phenylalanyl oligopeptide substrates. These non-basic ester-peptide pairs as well as the basic ester-peptide pair of arginyl derivatives, permits the direct comparison of the pH dependencies of the kinetic constants for the hydrolysis of those substrates by carboxypeptidase B. The data is interpreted in terms of three specific ionizing groups located at the active site of the enzyme. The mode and extent of inhibition of the hydrolysis of a specific substrate by another substrate was characterized kinetically. These results are discussed in relation to a proposed model for esterolytic and proteolytic action of carboxypeptidase B.

Animals↗
PubMed1975

A rapid method for measuring miotic activity of drugs in the intact mouse eye.

A rapid and precise method for evaluating the miotic activity of cholinergic drugs has been developed based on Long's method for measuring the rate of mydriasis. The rate of reversal of mydriasis developed previously in the intact mouse eye by a mild mydriatic (phenycyclidine) is used to evaluate the miotic activity. The method provides a useful tool for measuring and comparing the miotic activity of acetylcholine agonists and cholinesterase inhibitors.

Amides↗
PubMed1975

Drugs affecting the cholinergic system in the intact mammalian eye. I. Evaluation of the miotic activity of acetylcholine-like drugs in the mouse eye.

The effect of concentration and pH on the miotic activity of five acetylcholine-like drugs were studied in the intact mouse eye. The data suggests that it is mainly the nonionized form of the drug which contributes to its miotic activity. Acetylcholine-like drugs, degradable by cholinesterases, exert their miotic activity at higher concentrations than do those which are resistant to enzymatic hydrolysis. More active acetylcholine-like drugs appear to be less sensitive to concentration changes.

Acetylcholine↗
PubMed1974

Chemically modified nylons as supports for enzyme immobilization. Polyisonitrile-nylon.

Four-component condensations between amine, carboxyl, isocyanide and aldehyde lead to the formation of N-substituted amides (Ugi, 1962). The present paper describes the use of such condensations for the introduction of chemically reactive groups on to the polyamide backbone of nylon. Polyisonitrile-nylon was synthesized by partial hydrolysis of nylon-6 powder, followed by resealing of the newly formed -CO(2)... NH(2) (-) pairs via a four-component condensation, by using acetaldehyde and 1,6-di-isocyanohexane. Polyisonitrile-nylon could also be converted into a diazotizable arylamino derivative, polyaminoaryl-nylon, by a four-component condensation by using a bifunctional amine, pp'-diaminodiphenylmethane, in the presence of an aldehyde and a carboxylate compound. The versatility of four-component condensations involving the isocyanide functional group of polyisonitrile-nylon allowed coupling of proteins, in an aqueous medium at neutral pH, through either their amino or carboxyl groups. Trypsin and papain were bound to polyisonitrile-nylon through their amino groups by a four-component condensation by using acetaldehyde and acetate; conversely, succinyl-(3-carboxypropionyl-)trypsin, pepsin and papain were coupled through their carboxyl groups in the presence of acetaldehyde and an amine (Tris). Diazotized polyaminoaryl-nylon could be utilized for the immobilization of papain, via the tyrosine residues of the enzyme.

Chemical Phenomena↗