María Isabel Cornejo Plaza

Effect of manganese on the quaternary structure of human liver arginase

Abstract 1. 1. The molecular weight of human liver arginase ( l -arginine amidinohydrolase, EC 3.5.3.1) as determined by gel filtration was found to be 118 000. 2. 2. Incubation of the enzyme with EDTA followed by dialysis resulted in an inactivated enzyme with a molecular weight of about 30 000. It is suggested that the native enzyme is composed of four subunits. 3. 3. Addition of Mn 2+ to the inactive subunits resulted in the regeneration of the enzymatic activity. The molecular weight of the regenerated enzyme was found to be that of the native enzyme. 4. 4. The native enzyme and the subunits differ in ion exchange chromatography and electrofocusing behaviour.

Immunodiffusion studies on human liver and erythrocyte arginases.

Summary 1. Purified preparations of human liver and erythrocyte arginase ( L -arginine ureohydrolase, EC 3.5.3.1) injected to rabbits cause the formation of antibodies that precipitate the enzymic activity in homologous and heterologous antigens. The enzymic activity is not changed by these antibodies. 2. The experiments of double diffusion in agar suggest a total identity of the enzymic proteins in both antigens when they react with anti-E serum (immune serum prepared by injection of E antigen (purified erythrocyte arginase preparation)), but only partial identity when they react with anti-H serum (immune serum prepared by injection of H antigen (purified liver arginase preparation)). 3. Two enzymic protein fractions, with cationic charges at pH 8.6, were separated by electrophoresis in liver and erythrocyte antigens. The faster fraction (F) has 120–200 U/mg protein in liver preparations and 12–66 U/mg protein in red cells preparations and includes 90–95% of the total arginase activity. The slower fraction (S) has 2–9 U/mg protein in liver preparations and 0.3–1.2 U/mg protein in erythrocyte preparations. Fractions F and S in each antigen are precipitated by anti-H serum antibodies. In anti-E serum there are enough precipitating antibodies against S component but not against F. Anti-F antibody exists however in anti-E serum and has been concentrated in its γ 2 -globulin fraction. The position of the precipitation arcs of arginase formed in immunoelectrophoresis coincides with the zones of arginase activity separated by electrophoresis. 4. The comparison of the electrophoretic displacements, and the immunochemical reactions of the fast and slow migrating proteins indicate the presence of two corresponding and probably identical isozymes in both purified arginase preparations.

Molecular changes during the titration of α-keto-δ-aminovaleric acid☆

Abstract Titration of α-keto-δ-aminovaleric acid indicates the presence of two ionizable groups in the molecule with p K ′ 1.77 and 5.99. The first p K ′ corresponds to the COOH group. The second p K ′ is attributed to the ionization of the pyrrolinium structure of Δ 1 -pyrroline-2-carboxylic acid, the cyclic form of α-keto-δ-aminovaleric acid. This interpretation is supported by infrared spectroscopy of the solid compound isolated at pH 2.0 and 7.0. The existence of a pyrrolinium structure for Δ 1 -pyrroline-2-carboxylic acid is also supported by the results of ultraviolet spectra. The influence of pH on the condensation reaction of Δ 1 -pyrroline-2-carboxylic acid with o -aminobenzaldehyde, the nature of the derivatives formed in solutions of different pH by reduction with borohydride, and the increased susceptibility to N -acetylation of the form existing at low pH, are consistent with these structural deductions. The molecular extinctions of the colored compounds resulting from the reaction of pyrroline-2-carboxylic (α-keto-δ-aminovaleric) acid with acid ninhydrin and with o -aminobenzaldehyde were determined.

Blood arginase: its distribution in several vertebrate species.

Abstract 1. 1. Arginase activity is present in mensurable amounts in the erythrocytes of man, pig, cow and sheep, but is not detectable in the blood of several ureotelic and uricotelic vertebrates (mammals, birds and amphibia). It was only found in three of seven specimens of horse blood. 2. 2. In all species the blood arginase has never been found in plasma. 3. 3. Human blood arginase is only present in the erythrocytes. No enzyme activity is found in plasma, leucocytes, platelets and red cell stroma. Arginase appears to be located in the cytoplasma of erythrocytes but not in cell surface and membrane.

Non-enzymic transamination between ornithine and glyoxylate.

Abstract Ornithine and glyoxylic acid have been found to transaminate spontaneously. Heating the reaction mixture in the presence of aluminum ions results in a marked increase in the reaction rate. The reaction appears to be an α-transamination with the formation of glycine and α-keto-δ-aminovaleric acid; this latter compound is in equilibrium with its cyclic form Δ1-pyrroline-2-carboxylic acid (P-2-C). 2

El consentimiento informado en Psiquiatría. Una mirada desde el derecho en las legislaciones de Colombia, Chile y España

Este trabajo tiene como objetivo principal analizar algunos aspectos generales del consentimiento informado en la actividad clinica desde una optica eminentemente juridica y la forma como este opera en Colombia, Espana y Chile. Ademas, al final de este articulo se estudia si la infraccion del consentimiento informado por parte del medico encargado de la atencion del paciente con trastorno mental genera alguna infraccion a la lex artis, que podria eventualmente implicar responsabilidad penal por imprudencia de este profesional de la salud.

Characterization of cyclic nucleotide phosphodiesterases in Xenopus laevis ovary

A cGMP-stimulated cyclic nucleotide phosphodiesterase present in cytosol of Xenopus laevis ovary has been purified and characterized. A cAMP-specific phosphodiesterase which is not activated by either cGMP or calmodulin, has also been characterized. Brief exposure of intact oocytes to 10 micro M progesterone results in an increase in activity of the cAMP-specific enzyme. The cGMP-stimulated and the calmodulin-activated phosphodiesterases are not altered. Changes in cyclic nucleotide levels during progesterone-induced maturation of oocytes may be modulated by these isoenzymes.