The inhibition of urease and succinoxidase by metabolic products of p-dimethylaminoazobenzene and by some related amines

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Abstract
Quinone-forming amines strongly inhibited urease activity after exposure to air. Aniline and benzidine which were not readily oxidized were not inhibitory. Urease inhibiting amines also inhibited succinoxidase from rat livers, but with this enzyme system oxidation of amines (by cytochrome oxidase component) was so rapid that maximum inhibitory effect was observed with freshly prepared soln. while a previous exposure of amine soln. to air resulted in a decrease of activity. With the addition of cytochrome c, the higher conc, of the amines (10-3-10-4M) gave an initial increase of O2 uptake followed by complete inhibition, while lower conc. (10-5-10-6M) gave a gradually increasing inhibitory effect. Without added cytochrome c, high conc, of amines showed inhibition in only some livers while low conc, were often inactive. The initial increase in O2 uptake was due to catalytic oxidation of amines by the tissues and when the amines were added to the enzyme 20-30 mins. before the suc-cinate, complete inhibitory activity was observed immediately on addition of succinate. The succinoxidase of livers from animals which had been fed p-dimethylaminoazobenzene even in tumor-free portions of tumor-bearing animals showed the same behavior toward amines as controls.

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