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July 25, 1966


JAMA. 1966;197(4):292. doi:10.1001/jama.1966.03110040102024

Not so long ago cheese was found to interfere with monoamine oxidase inhibitors and to create severe adverse reactions in patients who had recently consumed a drug of this group and cheese. Now, cheese is in trouble again: this time it is the main cheese protein—casein.

Marrink and Gruber1 found that casein had considerable ribonuclease activity in 11 different commercial casein preparations tested. Ribonuclease of casein depolymerized ribonucleic acid in biochemcal substrates, which led to a false value of their proteolytic activity. Thus, casein should be avoided in determining proteolytic activity in tissue extracts. Especially, casein should not be used in Kunitz assay unless the ribonuclease activity in the casein has been completely destroyed beforehand.

It is clear that, at times, simple and apparently harmless items become important. Cheese itself remains a useful and nutritious product, but cheese, or casein, or other chemical substances entering into a reaction, but

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