Search PubMed⌕ Search

Biomedical subjects

M Maitre

Publications and source records attributed to M Maitre.

At least 109 records · Page 6Linked to original sources
PubMed1979

Comparison of high-affinity binding of [3H]GABA to subcellular particles of rat brain and liver.

The binding of [3H]GABA and retention of [14C]sucrose have been studied in freshly prepared "synaptosomal-mitochondrial" (P2) fractions of rat cerebral cortex and liver using bicarbonate-buffered medium (containing 147 mEq/liter of Na+), and in frozen/thawed crude membrane fractions of rat whole brain and liver using Na+-free Tris HCl medium. GABA-sensitive sites (GSS) and bicuculline-methiodide- (BMI-) sensitive sites (BMI-SS) were defined as those amounts of [3H]GABA that were sensitive to the displacement by 10(-3) M unlabeled GABA or BMI. In the presence of added Na+, two high-affinity GABA-binding processes were detected in the P2 fraction of cerebral cortex. The lower-affinity process (likely related mainly to uptake sites) had KB approximately equal to 10(-5) M, Bmax for GSS approximately equal to 3 nmol/mg protein, and Bmax for BMI-SS approximately equal to 0.5 nmol/mg protein, whereas the higher-affinity process (likely related to synaptic GABA receptors) had KB approximately equal to 10(-7) M, BMAX for GSS approximately equal to 43 pmol/mg protein, and BMAX for BMI-SS approximately equal to 2 pmol/mg proteins. Only the higher-affinity process was detected in the liver P2 fraction, and it had KB approximately equal to 3.7 x 10(-8) M, BMAX for GSS approximately equal to 0.48 pmol/mg protein, and BMAX for BMI-SS approximately equal to 0.1 pmol/mg protein (i.e., about 1/100 and 1/20 the receptive BMAX values of cerebral cortex). This binding process of the liver P2 fraction could represent sites involved in mitochondrial GABA transport. In Na+-free Tris HCl medium, high-affinity [3H]GABA binding appeared to exist in frozen/thawed membrane preparations of both brain and liver when data were expressed on a protein basis. However, this binding to liver membranes was not displaceable by 10(-5) M unlabeled GABA, and when these data were expressed on a weight basis and corrected for [3H]GABA present in trapped supernatant fluid of the pellets, no [3H]GABA binding was detected in the liver preparation.

Animals↗
PubMed1978

[Purification of 2 succinic semi-aldehyde reductases from the human brain].

Two succinic semi-aldehyde reductases (A and B) have been purified to electrophoretic homogeneity. Enzyme A, which is a monomer of molecular weight 40,000 +/- 5,000 reduces a wide range of aldehydes and is inhibited by some barbiturates and certain anticonvulsants. Enzyme B, which is a dimer of molecular weight 80,000 +/- 10,000, is very specific for succinic semi-aldehyde and is not inhibited by the aforementioned compounds.

Aldehyde Oxidoreductases↗
PubMed1978

Purification and properties of two succinate semialdehyde dehydrogenases from human brain.

In human brain there are two major isoenzymes of succinate semialdehyde dehydrogenase (succinate-semialdehyde: NAD+ oxidoreductase, EC 1.2.1.24). They are composed of two apparently identical subunits with a molecular weight of 69 000. The Km (limits) for their substrates NAD+ and succinate semialdehyde are 1.6.10(-5) M and 3.7.10(-6) M, respectively, for one enzyme, and 1.85.10(-5) M and 2.10(-6) M, respectively, for the other. These values, and other kinetic data obtained from the two enzymes are not very different. However the enzymes differ in the following respects: their behavior on ion exchange and 5'-AMP affinity columns, their isoelectric points, their tryptic fingerprints and in their amino acid compositions.

Aldehyde Oxidoreductases↗
PubMed1978

Comparison of the structural characteristics of the 4-aminobutyrate:2-oxoglutarate transaminases from rat and human brain, and of their affinities for certain inhibitors.

4-Aminobutyrate:2-oxoglutarate (4-aminobutyrate:2-oxoglutarate amino-transferase, EC 2.6.1.19) from human brain has been purified 2500-fold with respect to the initial homogenate. The enzyme, which appears to be pure by polyacrylamide gel electrophoresis, N-terminal analysis and immunodiffusion, was compared to rat brain 4-aminobutyrate transaminase, purified to the same extent in an earlier study [15]. The two enzymes, which have approximately the same molecular weight, show large differences in their tryptic fingerprints and in the peptides produced by cyanogen bromide cleavage. The Km values (limit) for 4-aminobutyrate are different, the human enzyme having four times greater affinity for this substrate. A series of branched-chain fatty acids (including n-dipropylacetate), which are structural analogues of 4-aminobutyrate and inhibit rat brain 4-aminobutyrate transaminase, are less powerful inhibitors of the human enzyme.

4-Aminobutyrate Transaminase↗
PubMed1978

Purification and some properties of L-glutamate decarboxylase from human brain.

Glutamate decarboxylase (EC 4.1.1.15) from human brain has been purified 8000-fold with respect to the initial homogenate. The molecular weight of the native enzyme was found to be 140000 by electrophoresis on a polyacrylamide gradient gel slab. The presence of a single protein band (Mr 67000) on sodium dodecylsulphate/polyacrylamide gel and the existence of only one N-terminal amino acid suggest that the enzyme consists of two similar if not identical polypeptide chains. The Km of the enzyme at the optimum pH of 6.8 is about 1.3 x 10(-3) M for glutamate and 0.13 x 10(-6) M for pyridoxal phosphate. The analysis of the effects of various inhibitors of mouse brain glutamate decarboxylase on the human enzyme confirms the strong competitive inhibition caused by 3-mercaptopropionic acid (Ki = 2.7 x 10(-6) M) while the Ki values for allylglycine and chloride ion are 1.8 x 10(-2) M and 2.2 x 10(-2) M, respectively.

Amino Acids↗
PubMed1977

Purification and properties of rat brain succinic semialdehyde dehydrogenase.

Succinic semialdehyde dehydrogenase from rat brain has been purified to electrophoretic homogeneity. It has a molecular weight of about 140, 000 and is composed of two apparently identical subunits. The reaction catalized by the pure protein is entirely dependent on endogenous --SH groups. The Kim (limits) for NAD and succinic semialdehyde are 2 X 10(-5) M and 1 X 10(-4) M respectively at the optimum pH of 8.6. Inhibition studies show that the reaction mechanism is a compulsory ordered on where NAD binds first followed by succinic semialdehyde.

Aldehyde Oxidoreductases↗