Identification of yeast phase of pathogenic fungi by the specificity of their aminopeptidase(s)

Specificity of aminopeptidase(s) was fluorimetrically determined in the yeast phase of Histoplasma capsulatum, H. duboisii, H. farciminosum, Blastomyces dermatitidis, Paracoccidioides brasiliensis, Candida albicans and Cryptococcus neoformans. After individually incubating each of 26 amino acid-βnaphthylamides with each yeast, the amount of each amino acid-βnaphthylamide hydrolyzed was determined by measuring the free naphthylamine. This resulted in a reproducible profile of the aminopeptidase(s) for each fungus when medium, growth time, size of inoculum and incubation period were standardized. This technique provided a rapid and specific means of identification and differentiation among these yeasts. Specific amino acids were identified from the profile of each yeast as those rapidly liberated by the aminopeptidase(s) of that yeast. These amino acids delineated the amino acid requirement for the normal growth of each yeast.