Breakdown of cozymase by a system from nervous tissue

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Abstract
The process by which tissue prepns. from the central nervous system liberate nicotinamide from cozymase proceeded at rates of 0.4-1.8 [mu]mol./ mg. dry wt./hr.; this was often greater than the rate of respiration by the tissue. The reaction approached its max. velocity at the natural concn. of cozymase in brain tissue (5 x 10-4[image]); half the maximum velocity was reached at less than 10-4[image] cozymase. The breakdown was very sensitive to nicotinamide; 10-3[image] nicotinamide reduced the rate of breakdown of 3 x 10-4 [image] cozymase to half its uninhibited value. The process resulted in the formation of one equivalent of acid/molecule of nicotinamide liberated. This was apparently due to the disappearance of the pyridinium ion, and when the reaction was carried out in NaHCO3-CO2 buffers its velocity could be followed readily manometrically by CO2 evolution. The optimum pH of the reaction was approx. 7, and the velocity was almost unaffected by many inorganic salts. The system responsible for the reaction remained associated with tissue debris in isotonic solutions, and was fairly stable at 0 or 37[degree], but inactivated rapidly at 70[degree]. It was easily obtained in water soln.
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