April 13, 2004
Peptides are susceptible to enzyme degradation in saliva, which renders them inactive or less active, but that is not the case with MUC7 12-mer-D, according to Bobek. "This peptide, in which D-amino acid derivatives are substituted for natural L-amino acids (producing a mirror image of the original), is not recognized and thus not broken down by protein-degrading enzymes in saliva," she said.
Bobek tested the peptide's activity in saliva and salt solutions containing C. albicans, and compared its fungicidal activity with MUC 12-mer, natural L form, the normal configuration of the peptide, which is active against C. albicans, but susceptible to enzyme degradation.
Results showed that in saliva at 100 micromolar concentration, the D peptide killed 95 percent of the organisms, while the L peptide killed only 56 percent. In the salt solution, at much lower concentration (25 micromolar), the D peptide killed 85 percent of the fungal agent, while the L form killed less than 20 percent. The D peptide was much less toxic than current treatments. Bobek noted that even at the relatively high concentration of 100 micromolar, the D peptide showed little red-blood-cell destruction, a standard toxicity measure. Next, Bobek will test the peptide in a mouse model of oral candidiasis.