PubMed Health⌕ Search

Biomedical subjects

M Busquets

Publications and source records attributed to M Busquets.

26 records · Page 2Linked to original sources
PubMed1987

A kinetic method for quantification of aspartate aminotransferase isoenzymes.

A spectrophotometric assay is proposed to determine the levels of aspartate aminotransferase (AAT) isoenzymes from chicken liver by a steady-state kinetic method which depends on the differential inhibition of these isoenzyme forms by high concentrations of substrate 2-oxoglutarate at pH 6.2. The use of a standard curve permits the determination of the percentage of chicken liver c-AAT and m-AAT isoenzymes. This method yields results in good correlation with those achieved by different extent adipate inhibition and by differential centrifugation.

Animals↗
PubMed1985

Separation and kinetic properties of the molecular forms of chicken liver cytoplasmic aspartate aminotransferase.

A method is proposed for the separation of the five molecular forms, alpha, beta, gamma, delta and epsilon, of chicken liver cytoplasmic aspartate aminotransferase free from lactate dehydrogenase activity. These molecular forms varied in isoelectric point, but no differences were observed either in their Michaelis constants or in the degree of their inhibition by excess of 2-oxoglutarate or L-aspartate.

Animals↗
PubMed1985

Effect of phosphate and other inorganic anions on the activity of chicken liver cytosolic aspartate aminotransferase.

Chicken liver aspartate aminotransferase was inhibited by several inorganic anions. The inhibitory effect of the anions was related to their chaotropic character. Apparent Km (2-oxoglutarate) and Km (L-aspartate) values depended on the molarity of the buffer. The profile of the curves obtained did not depend on the nature of the enzyme sample assayed. Phosphate slightly inhibited the holoaspartate aminotransferase and was a strong inhibitor of apoaspartate aminotransferase with respect to pyridoxal phosphate.

Animals↗
PubMed1985

Modification of the kinetic parameters of chicken liver cytoplasmic aspartate aminotransferase by lactate dehydrogenase.

A method for the purification of chicken liver soluble aspartate aminotransferase, lactate dehydrogenase free, is proposed. The preparation, which contained a mixture of the five molecular forms of the enzyme, showed a 120-fold increase in specific activity, with respect to the initial homogenates. Differences in Km(2-oxoglutarate) and saturating concentrations among solutions of purified enzyme and soluble fraction were due to the 2-oxoglutarate reductase activity of lactate dehydrogenase.

Animals↗
PubMed1978

[Kinetics of chicken liver mitochondrial and cytoplasmic glutamate oxalacetate transaminase (author's transl)].

Electrophoresis at pH 7.4, on cellulose polyacetate strips, and specific staining, show the occurrence of two molecular forms of the mitochondrial and soluble isoenzymes from chicken liver aspartate aminotransferase. The optimum pH of the cytoplasmic enzyme with L-aspartate and alpha-ketoglutarate as substrats is approximately 7, while the mitochondrial one is practically unaffected in the interval 6-8. The kinetic reactional mechanism is of ping-pong bi-bi type for both enzymes, as confirmed by the method of Garces-Cleland, and their inhibitions by excess of the substrates L-aspartate and alpha-Ketoglutarate are competitive, in accordance with the proposed mechanism.

Animals↗
PubMedDate not supplied

Graphical analysis of data from pharmacology experiments.

Dose-response curves are often used in the study of the interaction of hormones and receptors. From these plots, IC50 or EC50 values are calculated. In these pharmacological assays it is implicitly assumed that a single receptor predominates in a tissue. In this paper the interaction of a ligand with two receptors is studied from a theoretical point of view. It is assumed that the responses mediated by these receptors are qualitatively or quantitatively different. The theoretical direct and Scatchard plots display a high variety of shapes depending upon the difference in potency of the effect of the drug acting in both receptors and upon the magnitude and sign of the individual response. When dose-response curves taken from the literature have been transformed into direct or Scatchard plots new information has become available. With respect to this, it is shown that agonists of purinergic receptors seem to interact with two different populations of receptors. We claim that carefully designed experiments must provide valuable information concerning the number of subtypes of receptors present in a given system and the kind of response mediated by them.

Adenosine↗