Enzymic Activity of the K5-Type Yeast Killer Toxin and Its Characterization

Abstract

K5-type yeast killer toxin secreted by P. anomala NCYC 434 cells has a broad killing spectrum. Competitive inhibiton of killer activity showed that glucans, mainly the -1,3 glucan, represent the primary toxin binding site within the cell wall of sensitive cells. Its hydrolytic activity on laminarin in an exo-like fashion revealed that the toxin exerts its killing effect by exo--1,3-glucanase activity. Its specific activity on laminarin was 120 U/mg, and the Michaelis constants K m and V max for laminarin hydrolysis were 0.25 mg/ml and 370 mol/min/mg. The toxin exerted its cytocidal effect after 2 h contact with the target cells. Production of the toxin by the cells was induced only when they were grown in culture media rich in -glucan sources, and the addition of glucose increased the specific production rate. The enzymic activity of the toxin was fully inhibited by Hg þ2 , but increased with some other metal ions, most of all by Pb þ2 .

Stratum corneum lipid liposome-encapsulated panomycocin: preparation, characterization, and the determination of antimycotic efficacy against <em>Candida</em> spp. isolated from patients with vulvovaginitis in an in vitro human vaginal epithelium tissue model

“…15,16 In solution, panomycocin is stable and active at the pH range between 3.0 and 5.5 up to 37°C. 12,13 In lyophilized form, it retains its stability and activity up to 38.5°C (unpublished data) and in the vaginal pH range.…”

“…In various studies, panomycocin, which is produced and secreted into the environment by the killer (K+) yeast strain Wickerhamomyces anomalus (formerly known as Pichia anomala) NCYC 434, has been shown as a promising potential antifungal agent in biomedicine. [12][13][14] Panomycocin is a 49 kDa monomeric glycoprotein with an exo-β-1,3-glucanase activity. It hydrolyzes the exo-β-1, 3-glucans which are vital polymers for the integrity of the fungal cell wall, leading to the disruption of the cell wall and death of the target cells.…”

“…It hydrolyzes the exo-β-1, 3-glucans which are vital polymers for the integrity of the fungal cell wall, leading to the disruption of the cell wall and death of the target cells. 13 The mammalian cells lack the β-1,3-glucans in their structure, and this highlights the use of panomycocin as a selective antifungal/antimycotic agent in therapy. In several studies, the potent in vitro antifungal activity of panomycocin against human dermatophytes and Candida spp.…”

Yeast Killer Toxins: Fundamentals and Applications

“…Strain NCYC434 produces K5, a 49-kDa toxin alternativley termed panomomycin; it has exo-b-1,3-glucanase activity prefering pH values between 3.0 and 5.5 and temperatures up to 37 C (Izgü and Altinbay 2004;Izgü et al 2005). Such enzymatic activity and the acidic pH optimum reminds one of WmKT of W. saturnus var.…”

Isolation of Yeasts from Various Food Products and Detection of Killer Toxin Activity <i>In vitro</i>

“…This advantage has various scientific and commercial applications [5]. Killer yeasts have been used in biotyping of pathogenic yeasts as well have been proposed as antimycotic agents [6].…”