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M C Duque-Magalhães

Publications and source records attributed to M C Duque-Magalhães.

8 recordsLinked to original sources
PubMed1994

Identification, purification and partial characterization of a carboxypeptidase from the matrix of rat liver mitochondria: a novel metalloenzyme.

A novel carboxypeptidase has been purified to apparent homogeneity from the matrix fraction of rat liver mitochondria by using a procedure mainly based on immobilized-metal-affinity chromatography (IMAC). This carboxypeptidase has been named mCP-III, since it represents the third major peak of carboxypeptidase activity after the IMAC step of purification. mCP-III hydrolyses a number of N-blocked dipeptides, with preference for Cbz-Phe-Ala, and shows no degrading activity towards 125I-casein. The optimal pH of its activity is 7.6, the apparent Km for Cbz-Phe-Ala is 0.12 mM and the specific activity is 145.5 mumol/min per mg of protein. The enzyme is a typical metalloproteinase, is inhibited by 1,10-phenanthroline and carboxypeptidase inhibitor and re-activated by added Zn2+ and Co2+. The molecular mass estimated by molecular-sieve h.p.l.c. was approx. 115 kDa with two protein bands of 61 and 50 kDa shown by SDS/PAGE analysis, indicating that the enzyme is active as a dimer. This is the first clearly identified carboxypeptidase within mitochondria.

Animals↗
PubMed1990

Evidence for an acid phosphatase in African swine fever virus.

An acid phosphatase activity has been detected in purified preparations of African swine fever virus. Purified viral cores obtained after Nonidet-P40 and 2-mercaptoethanol treatment of the virus retained the activity as assayed with nitrophenyl phosphate as substrate at pH 5. Enzyme cytochemistry by electron microscopy showed that the acid phosphatase activity is localized mainly inside the core of the virion. The molecular weight and the isoelectric point of the virus acid phosphatase activity confirmed that it was distinct from the host cellular enzyme.

Acid Phosphatase↗
PubMed1989

Proteolytic enzymes in mitochondria.

The current interest in mitochondrial proteases is based on the recognition that these enzymes are actually involved in very important regulatory and metabolic roles inside the organelle. It has been formerly assumed that functions such as limited proteolysis, continuous turnover to regulate protein levels and selective elimination of defective and/or exceeding protein molecules, which have been clearly demonstrated in the intact cell, are likely to be operative within the physical boundaries of a well delimited organelle as the mitochondrion is. Consistent evidence has gradually accumulated on the existence of intramitochondrial proteolytic systems and this has led to a systematic search for the responsible proteases. The present discussion gives a brief up-to-date account of the existing information on mitochondrial proteolysis and describes the contribution to this field made by our own research.

Animals↗
PubMed1987

Regulation of mitochondrial proteolysis. Selective degradation of inner membrane polypeptides.

The in vitro degradation of respiratory chain polypeptide components by a proteinase associated with the intermembrane space fraction was studied in rat liver mitochondria. Differences in susceptibility to proteolysis were detected by gel analysis after electrophoretic separation of the degraded polypeptides. A 55 kDa subunit is protected from proteolysis by the ATP molecule.

Animals↗
PubMed1986

Discrimination of distinct proteinases at the four structural levels of rat liver mitochondria.

Rat liver mitochondrial fractions corresponding to four morphological structures (matrix, inner membrane, intermembrane space and outer membrane) contain proteinases that cleave casein components at different rates. Proteinases of the intermembrane space preferentially cleave kappa-casein, whereas the proteinases of the outer membrane, inner membrane and matrix fractions degrade alpha S1-casein more rapidly. Electrophoretic separation of the degradation products of alpha S1-casein and kappa-casein in polyacrylamide gels shows that different polypeptides are produced when the substrate is degraded by the matrix, by both membranes and by the intermembrane-space fraction. Some of the degradation products resulting from incubation of the caseins with the mitochondrial fractions are probably the result of digestion by contaminating lysosomal proteinase(s). The matrix has a high peptidase activity, since glucagon, a small peptide, is very rapidly degraded by this fraction. These observations strongly suggest that distinct proteinases, with different specificities, are associated respectively with the intermembrane space and with both membrane fractions.

Animals↗
PubMedDate not supplied

[Intracellular proteolysis].

This article is intended to give an overview of the most significant facts in the area of intracellular proteolysis. It begins with general considerations on the importance and nature of the intracellular proteolytic processes and examples are given of what takes place during both the extensive proteolysis and the limited cleavage of the cellular proteins. We have mentioned the intracellular proteases that have been identified and their established role since the knowledge of the proteases involved in important to understand the mechanisms of these processes.

Adenosine Triphosphate↗