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Purification and characterization of secretory proteinase of Candida albicans
T Yamamoto1, K Nohara, K Uchida
1Alcoholic Beverages Research Laboratories, Takara Shuzo Co., Ltd., Shiga, Japan.
Abstract:
Proteolytic activity of medically important yeasts was tested in both YCB-BSA agar and medium. All of 134 strains of Candida albicans, 13 of 18 strains of Candida tropicalis and 11 of 18 strains of Candida parapsilosis had this activity, while none of 52 Candida glabrata strains or of 11 Cryptococcus neoformans strains tested had proteolytic activity. Strains of C. albicans fell into five groups based on the level and time-course of in vitro proteinase productivity. Five strains randomly selected from each group were tested for pathogenicity in mice. The strain possessing the strongest pathogenicity was used to purify proteinase. The molecular weight of the proteinase was approximately 44,000 daltons and its isoelectric point was pH 4.2. Optimal pH of the proteinase was 3.2 and the enzyme was stable below pH 7.0 and lost its activity above pH 8.0 at 37 C in a 60-min incubation. The 23 amino acid sequence of the proteinase N-terminus was determined.
Insights
Medically important yeasts, particularly Candida albicans, exhibit proteolytic activity. This study characterized a specific proteinase from a pathogenic Candida albicans strain, revealing its molecular properties and N-terminal sequence.
Area of Science:
- Medical Mycology
- Enzymology
- Biochemistry
Background:
- Proteolytic enzymes secreted by yeasts can contribute to pathogenicity.
- Understanding yeast proteolytic activity is crucial for diagnosing and treating fungal infections.
Purpose of the Study:
- To assess the proteolytic activity of medically important yeasts.
- To characterize the proteinase produced by pathogenic Candida albicans strains.
Main Methods:
- Testing yeast strains for proteolytic activity using YCB-BSA agar and medium.
- Purification and characterization of proteinase from Candida albicans.
- Determination of proteinase molecular weight, isoelectric point, optimal pH, stability, and N-terminal amino acid sequence.
Main Results:
- Candida albicans, Candida tropicalis, and Candida parapsilosis showed proteolytic activity, while Candida glabrata and Cryptococcus neoformans did not.
- Candida albicans strains were grouped by proteinase productivity and pathogenicity in mice.
- A proteinase with a molecular weight of ~44,000 Da, pI of 4.2, and optimal activity at pH 3.2 was purified and characterized.
Conclusions:
- Proteolytic activity is common in certain pathogenic yeasts, notably Candida albicans.
- The characterized proteinase is a key virulence factor, with defined biochemical properties.
- Further research into this proteinase may offer therapeutic targets for candidiasis.