A Heat-Stable Catalyst in Animal Tissues which destroys the Iminazole Ring and Unmasks Amino Groups.

AN account of the catalytic destruction of carnosine in vitro at 1000 by a substance present in skeletal muscle and liver has been previously published [Clifford, 1922]. These experiments showed a progressive loss of the iminazole ring when a solution containing carnosine was kept with skeletal muscle or liver over a period of 3-4 weeks. The amount of iminazole was estimated by a colorimetric method described previously [Clifford, 1921, 1], depending on the coupling of the histidine molecule of carnosine with diazo-reagent. The loss of red colour could be accounted for in two ways. The ring substance might have been joined to others in a more complicated manner, similar to that of the histidine in proteins, and thus be unable to couple with the reagent. Another and more probable solution was that the catalyst actually broke up the ring into some simpler substance. In the latter case it was possible that the nitrogen of the ring would be converted to amino nitrogen and then the increase of amino nitrogen could be estimated by van Slyke's method. Accordingly experiments were carried out in which parallel estimations of diazotisable iminazole and amino nitrogen were made.