The hœmatin content of horseradish peroxidase

Abstract

A number of preparations of horseradish peroxidase were made in various ways and the hematin contents and enzyme activities estimated. Though a marked parallelism between hematin content and activity was at first found, this was broken in products of higher activity. Further, the amount of hematin-iron present in these preparations of medium activity was far higher than the hematin or even total Fe content found by other workers in highly active preparations. Contrary to the supposition of Kuhn, Hand, and Florkin, no simple relation between hematin content and activity exists. In all the preparations from the lowest to the highest activity obtained, the whole hematin was present in the free state as acid hematin. No combination of the free hematin with nitrogenous substances present in the preparations is found below pH 9 and complete combination is only obtained above pH 10.5, at which alkalinity the enzyme is nearly inactive.