Observations on endopeptidases in human carious dentin

abstract – The enzymatic hydrolysis of hemoglobin (Hb) and N-α-benzoyl-DL-arginine-2-naphthylamine (BANA) was observed both in sound- and in carious human dentin. The enzyme activity expressed per mg protein in the sample and per min was at least ten times higher in carious than in sound dentin, as was also the DNA content in the samples. The hydrolysis of Hb and BANA was high over a relatively wide pH range, the optimum pH being 5.5 with Hb, and 7.0 with BANA, as substrates. EDTA, cetylpyridinium chloride and Hg²⁺ ions inhibited strongly the hydrolysis of BANA at pH 7.0 but only slightly at pH 10.4. The origin of these endopeptidase-like enzymes was thought to be mainly microbial. These enzymes were thought to hydrolaze proteins of the organic stroma of dentin during the carious process.