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Molecular expression of xylanase gene in Cryptococcus albidus
Biochimica Et Biophysica Acta
|December 18, 1985
Summary
Cryptococcus albidus requires an inducible endoxylanase enzyme for xylan utilization. This enzyme is synthesized as a precursor with a signal sequence, and its messenger RNA is only present in xylan-grown cells.
Area of Science:
- Microbiology
- Enzymology
- Molecular Biology
Background:
- Xylan, a complex polysaccharide, serves as a carbon source for some microorganisms.
- The yeast Cryptococcus albidus utilizes xylan, necessitating specific enzymatic machinery.
Purpose of the Study:
- To investigate the enzyme responsible for xylan degradation in Cryptococcus albidus.
- To characterize the synthesis and molecular properties of the xylan-degrading enzyme.
Main Methods:
- Monitoring endoxylanase induction via immunoprecipitation.
- Chemical deglycosylation using trifluoromethanesulfonic acid.
- In vitro translation of yeast RNA using a rabbit reticulocyte system.
Main Results:
- A highly glycosylated endoxylanase (48,000 Da) is secreted by C. albidus.
- Deglycosylation reduced the molecular weight to 40,000 Da.
- Tunicamycin treatment yielded a 40,000 Da polypeptide, indicating glycosylation.
- Xylanase mRNA was detected only in xylan-induced cells, translating to a 44,000 Da precursor polypeptide.
Conclusions:
- Xylan utilization in C. albidus depends on an inducible, secreted endoxylanase.
- The enzyme is synthesized as a precursor (44,000 Da) with a 35-residue signal sequence.
- Post-translational glycosylation increases the mature enzyme's molecular weight to 48,000 Da.