Assessment of carboxyl esterase activity in clinical isolates of Candida albicans

Introduction and objective: Esterase activity is used in evaluation and correlation of strains in fungi. Our previous study showed that Candida albicans has a kind of intracellular esterase activity in yeast extract, peptone, and glucose medium (YPG).The aim of this research was to study the qualitative and quantitative differences of this enzymatic activity among clinical isolates of this yeast.

Materials and methods: Candida albicans isolates which have been kept on Sabouraud dextrose agar medium by continuous passage were grown in YPG medium for 48h in order to induce enzymatic production. In the next step, yeast cells were collected and then broken with glass bead. Esterase activity of cytoplasmic extract of isolates was measured by colorimetric method. Besides, five synthetic substrates were used to assess the qualitative differences in this enzymatic activity.

Results: The cytoplasmic extract of 12 C. albicans isolates demonstrated an esterase activity to all used substrates and no significant qualitative and quantitative differences were found in this enzymatic activity. The average enzymatic activity of all isolates had a reversed relation to the number of carbon atoms in carboxyl substrates (except for alpha-naphtyle laurate). The amount of this activity for alpha-naphtyle acetate, beta-naphtyle acetate, alpha- naphtyle caprilate, alpha- naphtyle laurate, and alpha-palmitate were 14.4, 8.45, 0.94, 0.42, 0.75 unit (µM/mg protein in min), respectively.

Conclusion: The observed fluctuation in esterase activity of clinical isolates of C. albicans might be useful in tracking its sub species in epidemiological purposes.