Peroxidases metal content

The iron content of the body is 4—5g. Most of it is present in the hemoglobin (blood) and myoglobin (muscle tissue) pigments. The metal is also present in a number of enzymes (peroxidase, catalase, hydroxylases and flavine enzymes), hence it is an essential ingredient of the daily diet. The iron requirement depends on the age and sex of the individual, it is about 1.5-2.2 mg/day. Iron supplied in the diet must be in the range of 15 mg/day in order to meet this daily requirement. The large variation in intake can be explained by different extents of absorption of the various forms of iron present in food (organic iron compounds vs simple... 

It is evident that, because of its H2O2 content, guaiac cannot discriminate between peroxidase and oxidase action and, even worse, that a great number of metal ions and other compounds give a positive test in the absence of all enzymes. Therefore, guaiac should no longer be used for the assay of oxidative enzymes. 

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