PubMed Health⌕ Search

Biomedical subjects

M Ledig

Publications and source records attributed to M Ledig.

At least 73 records · Page 4Linked to original sources
PubMed1977

Free amino acid pool in the brain of mice homozygous for the gene "dilute lethal".

The neurologic mutant "dilute lethal" (dl) mice, which reveal several neurologic and biochemical disturbances similar to human phenylketonuria, were used to investigate some aspects of amino acid disorder. We have studied the free amino pool in the brain of "dl" mice and of their control littermates as well as phenylalanine and tyrosine levels in brain and liver as a function of age and after phenylalamine overload. The tyrosine level decreased in brain and liver of affected mice whereas the phenylalanine/tyrosine ratio increased as a function of age. The significantly higher phenylalanine level and phenylalanine/tyrosine ratio in the liver of 20-day-old "dl" mice suggest a lower liver phenylalanine hydroxylase activity. After phenylalanine overload, the impairment of phenylalanine metabolism is predominant in the brain of "dl" mice, suggesting a disturbance in phenylalanine hydroxylation. A decrease in the level of several amino acids occurs in the brains of "dl" mice without or after phenylalanine overload; these facts might correspond to a disturbance in the transfer of amino acids to the brain and may lead to impairment in protein synthesis.

Amino Acids↗
PubMed1976

Studies of soluble rat liver mitochondrial acid ATPases. I. Purification and catalytic properties of ATPase 1.

A method for isolation of a soluble ATPase from rat liver mitochondria after freeze thaw cycling is described. Two enzymatically active fractions were separated by DEAE-cellulose chromatography (ATPase 1 and ATPase 2). ATPase 1 has been purified 300 fold. ATPase 1 was homogenous as judged by polyacrylamide gel electrophoresis. The optimum pH of the enzyme was 5.8-6.0 and the optimum temperature was 45 degrees C. The enzyme follows Michaelis-Menten kinetics: Km (9 X 10(-4) M), Vmax (23,6 mumoles Pi released X min -1 X mg protein -1). The enzyme hydrolysed nucleoside triphosphates, but was inactive upon nucleoside di and monophosphates, glucose 6-phosphate, phosphoserine, pyrophosphate and glycerol 2-phosphate. In contrast to membrane bound ATPase, cations have no effect on the enzyme activity. Nucleoside di and mono phosphates and glycerol 2 phosphate inhibited competitively the enzyme. The enzyme was not affected by oligomycin, but was stimulated by lactate, 2-mercaptoethanol and dithiothreitol.

Adenosine Monophosphate↗
PubMed1975

Phosphopeptide and phosphoprotein metabolism in brain.

Phosphopeptide and phosphoprotein phosphorylation was studied in rat brain microsomes and rat brain slices which were incubated in the presence of [gamma-32 P] ATP under various experimental conditions. Radioactive phosphoserine was isolated from phosphopeptides and phosphoproteins. Naplus, K+, Mg2+ and cyclic AMP had a stimulating effect on the labelling of phosphopeptides. Ouabain and Ca2+ lowered the level of 32P incorporation into the phosphopeptides. The phosphoproteins behaved similarly to the phosphopeptides except for the potassium effect. Chase experiments showed a faster decrease in the labelling of phosphopeptides than in phosphoproteins. We suggest that both compounds may be involved in active transport phenomena.

Adenosine Triphosphate↗