Steroid hormone signalling system and fungi.

Three components of the steroid hormone signalling system, 17 beta-hydroxysteroid dehydrogenase, androgen binding proteins and steroid hormone signalling molecule testosterone were determined in the filamentous fungus Cochliobolus lunatus for the first time in a fungus. Their possible role in C. lunatus is discussed in comparison with their role in mammalian steroid hormone signalling system.

Isolation and identification of testosterone and androstenedione in the fungus Cochliobolus lunatus.

The cytosol of the filamentous fungus Cochliobolus lunatus was found to contain binding proteins for testosterone and androst-4-ene-3,17-dione. Both of these steroids were also found to be good exogenous substrates for the constitutive 17 beta-hydroxysteroid dehydrogenase, also found in this fungus. We were looking for the possible endogenous substrate.

Androgen binding proteins in Cochliobolus lunatus.

Testosterone and 4-androstene-3,17-dione (androstenedione) binding proteins were found in the cytosol of Cochliobolus lunatus, a filamentous fungus. The maximal androgen binding occurred by 120 min at 0 degrees C. Androgen binding proteins were degraded by protease treatment and at high temperature.

Involvement of the cell wall ofNocardia restricta on the bioconversions of steroid sapogenins.

The bioconversion of tigogenin, (25R)-5α-spirostan-3β-ol byNocardia restricta to (25R)-4-spirosten-3-one and (25R)-1,4-spirostadien-3-one was strongly increased using protoplasts instead of intact cells. The same effect could be achieved by addingβ-cyclodextrin to the medium. Since 5β-steroid sapogenins pass through the cell wall without hindrance, it can be concluded that the cell wall ofNocardia restricta is a rate-limiting factor only for 5α-isomers.

Hydroxylation of steroids with nonpolar side chains with 11 alpha-hydroxylase of Rhizopus nigricans.

Steroids with nonpolar side chains with 2, 4 and 8 C atoms were used as substrates for the 11 alpha-hydroxylase of Rhizopus nigricans. Their bioconversion was compared to that of progesterone, which was found to be far the best substrate giving the highest total bioconversion. 3-keto-4-ene steroids with nonpolar side chains were converted to their hydroxylated products in a small yield or not at all.