Avtor/Urednik		Kunič, Barbara
Naslov		Primerjava dveh monooksigenaznih sistemov s citokromom P450 v filamentozni glivi Rhizopus nigricans
Tip		monografija
Kraj izdaje		Ljubljana
Založnik		Medicinska fakulteta
Leto izdaje		1998
Obseg		str. 69
Jezik		slo
Abstrakt		Cytochromes P450 function as terminal oxidases in multicomponent monooxygenase systems. These systems participate in the biosynthetic processes as well as in the reactions necessary for the adaptation of an organism to changes in the environment. Besides the progesterone inducible steroidal hydroxylase which catalyses the transformation of progesterone to 11lalpha-hydroxyprogesterone we successfully confirmed the presence of another monooxygenase system in filamentous fizngus Rhizopus nigricans. This was lanosterol demethylase which participates in biosynthesis of ergosterol, a crucial component of cell membranes in fungi. Lanosterol demethylase was not inducible with progesterone; the enzyme activities of the progesterone induced and noninduced fungus were the same. In consistence with results obtained for other organisms the presence of lanosterol demethylase was confirmed in microsomal fraction of fungus Rhizopus nigricans. Using different chromatographic techniques cytochrome P45011alpha was partly purified from fiuigus Rhizopus nigricans and its activity was confirmed by in vitro reconstitution of steroidal hydroxylase. In the reconstitution experiment partly purified NADPH-cytochrome P450 reductase from fixngus Rhizopus nigricans was used. To find out how to differentiate between the hydroxylase and demethylase systems the influence of inhibitors ketoconazole and metyrapone on both monooxygenase systems was studied. Both substances effciently inhibited the steroidal hydroxylase and both induced type II difference spectra with the enzyme. No difference in ketoconazole induced type II difference spectra of the samples prepared from progesterone induced and noninduced fungus was observed. On the other hand metyrapone induced type II difference spectra were evidently different in progesterone induced and noninduced fungal preparations. (Abstract truncated at 2000 characters)
Deskriptorji		RHIZOPUS CYTOCHROME P-450 STEROID HYDROXYLASES PROGESTERONE ERGOSTEROL KETOCONAZOLE METYRAPONE HYDROXYPROGESTERONES NADPH-FERRIHEMOPROTEIN REDUCTASE LANOSTEROL