Author/Editor		Vitas, Marko
Title		Biotransformacija steroidov z glivo Cochliobolus lunatus in kvasovko Saccharomyces cerevisiae
Type		monografija
Place		Ljubljana
Publisher		Medicinska fakulteta
Publication year		1999
Volume		str. 121
Language		slo
Abstract		Steroid hydroxylations by the filamentous fungi including 11beta-hydroxylation are economically important for the production of corticosteroids, and were among the first examples of commercial biotransformations. The enzymes responsible are from the cytochrome P450 superfamily, but despite their importance little is known of their normal physiological role, properties or genes encoding them. This is due in the part to difficulties associated with their isolation, low specific content of protein, and the presence of multiple P450s making purification difficult to assess. Filamentous fungus Cochliobolus lunatus is an important hydroxylator of steroids at the 11beta-position which is required for corticoid activity. We investigated the hypothesis that the endogenous role of the commercially important inducible steroid hydroxylase cytochrome P450s of fungi was in defense against plant toxophores/secondary metabolites. Two plant defence compounds, the aglycones tomatidine and solanidine, the steroidal glycoalkaloid a-tomatine and the triterpene saponin beta-escin were tested as inducers of 11beta/14alfa-steroid hydroxylase in the filamentous fungus C. lunatus which is parasitic on important cereal crops and wild grasses. The extracts of saponins from the roots of Primula veris and green oat leaves were also tested as inducers of 11beta/14alfa-hydroxylation activity in progesterone biotransformation with the same fungus. Induction of steroid hydroxylase and inhibition of activity in some cases support our hypothesis that their endogenous function is in biochemical defence against secondary metabolites. In addition, in the same fungus sodium benzoate and L-phenylalanine did not enhance 11beta/14alfa-hydroxylation of sterods. However, C. lunatus as soil fungus was found to hydroxylate sodium benzoate to 4-hydroxybenzoate. (Abstract truncated at 2000 characters).
Descriptors		STEROIDS ASCOMYCETES BIOTRANSFORMATION SACCHAROMYCES CEREVISIAE CULTURE MEDIA SAPONINS CYTOCHROME P-450 POLYMERASE CHAIN REACTION DNA POLYMERASES DNA, FUNGAL SODIUM BENZOATES STEROID HYDROXYLASES GENE LIBRARY BASE SEQUENCE