LOCALIZATION OF ENZYMES IN NERVES. II. RESPIRATORY ENZYMES

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Abstract
In the head ganglion of the squid the cytochrome oxidase conc. was remarkably high, the Qo2 at 23[degree] C being -9.0 to -13.0. In the axoplasm extruded from the trunk containing the giant axon the conc. was lower, but relatively high compared with that of the remaining tissue. This finding was evidence for the previous assumption that the bulk of the respiratory enzymes was confined to the axoplasm while in contrast practically all of the choline esterase was found at the neuronal surface. Oxidation of pyruvic acid in the minced head ganglion occurred at a rate similar to that of p-phenylenediamine, the Qo2 being about[long dash]7.0 to[long dash]9.0. In a ground suspension of the head ganglion the activity of pyruvic oxidase fell off rapidly even if the following substances known to be of consequence in pyruvic acid oxidation were added: cytochrome c, adenosinetriphosphate, diphosphothiamin, diphosphopyridine nucleotide and succinate. In the axoplasm the activity of pyruvic oxidase was small, although in the whole trunk if minced, the rate of O2 uptake was about the same with pyruvate as with p-phenylenediamine. The axoplasm dissolved rapidly in isotonic soln. Therefore, the low Qo2 values must be attributed to the rapid loss of activity if the cell structure was destroyed. Pyruvic dehydrogenation was strongly increased in the presence of diphosphothiamin. In view of the conc. of this coenzyme at the neuronal surface thia incomplete breakdown, yielding acetic acid and CO2, might be of significance for the formation of acetylcholine.