The production of amino acids by cell fractions, particularly rat-liver mitochondria

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Abstract
Rat-liver mitochondria release amino acids (ninhydrin-positive material other than ammonia and peptides) when incubated at various temperatures and pH values. Anerobic production at 40[degree] and pH 7.4 was 0.152 [mu]mole/mg. dry weights/hour (range 0.070-0.300), and aerobically, 0.144 [mu]mole/mg dry weights/hour (range 0.061-0.221). Amino acids were also liberated at 0[degree] (qamino acid 0.012-obically). The production was linear with time. The rate of amino acid production varied inversely with the solute concentration. The absolute rate depended on the nature of the solute, ranging from qamino acid 0.595 with 12.5 m[image]-tris to 0.055 with 250 m[image]- phosphate. Amino acid production in-creased as the pH was lowered. This was probably due to different enzyme systems with different pH optima. Amino acid production varied with the type of buffer used in the incubation medium. The maximum rate was found with glyoxaline buffer (qamino acid 0.320 aerobically) and the minimum with pyro-phosphate buffer (aerobic qamino acid 0.022). Disrupted mitochondria gave higher qamino acid values than undamaged mitochondria (increase of 50-100%). This suggested that the proteolytic enzymes are soluble and intra-mitochondrial. The presence of substrate aerobically loweredqamino acid values, the maximum inhibition of production being 50%. All fractions of the rat-liver cell produced amino acids both aerobically and anaerobically at pH7.4 and 6.2. "Fluffy layer", incubated aerobically, was the most active fraction at both pH values. Mitochondria from other tissues and species (rat brain; sheep liver, brain, kidney and spleen; ox heart; pigeon breast muscle) all produced amino acids when incubated under the same conditions as rat liver, to the greatest extent in rat brain (anerobic qamino acid 0.125) and the least in ox heart (anerobic qamino acid 0.004).