Author/Editor		Lenasi, Helena
Title		Induction of 11alpha-steroid hydroxylating enzymes in filamentous fungus Rhizopus nigricans by tomatidine and Primula veris root extract: possible involvement of progesterone-binding molecules
Type		članek
Source		In: Kreft I, Škrabanja V, editors. European scientific symposium Molecular and genetic interactions involving phytochemicals. COST 916 action: bioactive plant cell wall components in nutrition and health; 2000 Sep 17-20; Gozd Martuljek. Ljubljana: Biotehniška fakulteta,
Publication year		2001
Volume		str. 187-93
Language		eng
Abstract		It is known that filamentous fungus Rhizopus nigricans is able to grow on several gathered products. In order to survive in sometimes hostile environment the fungus has evolved different defence metabolis pathways including steroidal hydroxylating enzyme system, which renders their substrates into less toxic compounds. Hydroxylating enzymes could be induced by some mammalian steroidal hormones and by some plant protective compounds, saponins. The mechanism of the induction process is not known but some evidence indicates that progesterone binding molecules could be involved in the induction by progesterone. In the present work we attempted to find out whether the same molecules are also involved in the induction of hydroxylating enzymes by saponins. The induction was performed using 15 micro M concentration of inducers, progesterone, tomatidine, tomatine and Primula veris root extract and 11alpha-hydroxylase activity measured using progesterone as substrate. The induction of hydroxylation enzymes reached the highest level when prosterone was used as inducer (29%), followed by tomatidine (11%), whereas the enzyme activity remained near the constitutive level after treatment of Rhizopus nigricans with tomatdine and Primula veris root extract. Progesterone binding molecules were determined in the plasma membrane fraction and in the cytosol of Rhizopus nigricans by competitive binding assay using (3H)- and (1H)progesterone. The affinity of tomatidine, tomatine and substances from Primula veris root extract for progesterone binders was tested by displacement studies. In the plasma membrane fraction all tested compounds acted as weak competitors when compared to unlabeled progesterone. In the cytosol the competition ability of tomatidine was higher but never reached the value of nonlabeled progesterone. (Abstract truncated at 2000 characters).
Descriptors		RHIZOPUS TOMATINE PROGESTERONE PLANT EXTRACTS STEROID HYDROXYLASES BINDING, COMPETITIVE BINDING SITES CYTOSOL