Biomedical subjects

M A Valenzuela

Publications and source records attributed to M A Valenzuela.

57 records · Page 4Linked to original sources

PubMed1973

Effects of protein-modifying reagents on an isoenzyme of potato apyrase.

Treatment of an isoenzyme of potato apyrase of high adenosine triphosphatase/adenosine diphosphatase (ATPase/ADPase) ratio with iodine, N-acetylimidazole or tetranitromethane inactivates the ATPase activity of this enzyme faster than its ADPase activity. There was protection by substrates with the two last-named substances. This and the appearance of nitrotyrosine suggests the participation of tyrosyl residues in both enzymic activities of potato apyrase. The participation of thiol groups is excluded by the insensitivity of apyrase to p-chloromercuribenzoate. Also, 2-hydroxy-5-nitrobenzyl bromide or carboxymethylation produce the same rate of inactivation of ATPase and ADPase activities. Substrates protect both activities from inactivation. Hydrogen peroxide and photo-oxidation inactivate ATPase activity faster than ADPase activity. There is no protection by substrates. Analysis of pH effects on V(max.) and K(m) suggest different pK values for the amino acid residues at the ATP and ADP sites.

Acylation↗

PubMedDate not supplied

A comparative study of fish species identification by gel isoelectrofocusing two-dimensional gel electrophoresis, and capillary zone electrophoresis.

A comparative study of fish species identification was accomplished using three different electrophoretic techniques. Sarcoplasmic proteins were extracted from three related fish species and subjected to gel isoelectrofocusing (IEF), two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and capillary zone electrophoresis (CZE). The fish species--Genypterus chilensis, Genypterus blacodes, and Genypterus maculatus--were from the Ophidiidae family. The three electrophoretic techniques provided suitable fish species identification. Nevertheless, CZE demonstrated several advantages over the other two conventional techniques. Some of the benefits include the use of small amounts of reagents; short separation times, permitting fast comparative analysis; data reproducibility; and ease with which the technique is performed.

Animals↗

PubMedDate not supplied

Matrix metalloproteinase profile in patients with Creuztfeldt-Jakob disease.

Preliminary findings suggest that abnormalities in matrix metalloproteinase (MMP) activity may be found in the cerebrospinal fluid (CSF) of patients with Creutzfeldt-Jakob disease (CJD). In this study of 16 subjects with CJD and 16 age-, and sex-matched controls, we determined the presence of MMP-2 and MMP-9 in their active and proenzyme forms, the relative levels of MMP-3 and four inhibitors of MMP activity (TIMP-1, TIMP-2, TIMP-3 and TIMP-4), and the concentration of 4-3-3 protein. The methodology used involved zymography and immunological techniques. The results indicate that, compared with controls, CJD patients have a significantly higher positive frequency of pro-MMP-9 and of the active form of MMP-2, along with significantly higher levels of TIMP-1 and TIMP-2, classical inhibitors of MMP-9 and MMP-2, respectively. We also found a positive correlation between 14-3-3 protein concentration and that of TIMP-1 and TIMP-2 levels (correlation coefficients of 0.793 and 0.798, respectively). These results suggest that abnormalities in MMP and TIMP profiles may be helpful in the biochemical characterisation of CJD.

14-3-3 Proteins↗