Fungal 17 beta-hydroxysteroid dehydrogenase.

Area of Science:

• Mycology
• Biochemistry
• Enzymology

Background:

• Steroid metabolism is crucial in many organisms.
• Hydroxysteroid dehydrogenases (HSDHs) play key roles in steroid transformations.
• Fungal HSDH activity and its specific roles remain underexplored.

Purpose of the Study:

• To investigate the presence and characteristics of 17 beta-hydroxysteroid dehydrogenase (HSDH) activity in diverse fungal species.
• To determine the regioselectivity and pathway preference (oxidative vs. reductive) of fungal HSDHs.
• To explore the potential ecological or metabolic significance of HSDH in fungi.

Main Methods:

• Testing constitutive 17 beta-HSDH activity in fungal isolates from various taxonomic classes.
• Assessing enzyme regioselectivity for the C17 position of steroid substrates.
• Detecting 20 beta-HSDH activity in specific fungal strains.
• Comparing the rates of oxidative and reductive pathways catalyzed by the enzyme.

Main Results:

• Constitutive 17 beta-HSDH activity was detected in all tested fungal representatives across different classes.
• The enzyme exhibited regioselectivity for the C17 position of the steroid ring.
• 20 beta-HSDH activity was specifically identified in *Trichoderma viride*.
• The oxidative pathway was favored over the reductive pathway in most fungal species examined.

Conclusions:

• Fungi possess widespread 17 beta-HSDH activity, suggesting a conserved role in steroid processing.
• Fungal HSDHs are primarily C17-acting enzymes, with potential for specific isoforms like 20 beta-HSDH.
• The prevalence of the oxidative pathway indicates its importance in fungal steroid biotransformation.