PubMed HealthSearch

PubMed · 945258

Pleuromutilins. Fermentation, structure and biosynthesis.

Abstract

Derivatives of pleuromutilin, formed during the fermentation of pleuromutilin, were isolated and their structure determined. 14-Acetyl-mutilin and mutilin as well as different unsaturated fatty acid esters of pleuromutilin were identified. The proportion of each derivative formed depends to a considerable degree on the conditions of the fermentation process. The possible biosynthetic pathways are shown.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

F Knauseder, E Brandl. 1976. Pleuromutilins. Fermentation, structure and biosynthesis.. https://doi.org/10.7164/antibiotics.29.125

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Kinetic study of the oxidation of 3-hydroxyanisole catalysed by tyrosinase.

Tyrosinase hydroxylates 3-hydroxyanisole in the 4-position. The reaction product accumulates in the reaction medium with a lag time (tau) which diminishes with increasing concentrations of enzyme and lengthens with increasing concentrations of substrate, thus fulfilling all the predictions of the mechanism proposed by us for 4-hydroxyphenols. The kinetic constants obtained, kcatM = (46.87 +/- 2.06) s-1 and KmM = (5.40 +/- 0.60) mM, are different from those obtained with 4-hydroxyanisole, kcatM = (184.20 +/- 6.1) s-1 and KmM = (0.08 +/- 0.004) mM. The catalytic efficiency, kcatM/KmM is, therefore, 265.3 times greater with 4-hydroxyanisole. The possible rate-determining steps for the reaction mechanism of tyrosinase on 3- and 4-hydroxyanisole, based on the NMR spectra of both monophenols, are discussed. These possible rate-determining steps are the nucleophilic attack of hydroxyl's oxygen on the copper and the electrophilic attack of the peroxide on the aromatic ring. Both steps may be of similar magnitude, i.e. take place in the same time scale.

Agaricales

Concentrations of mercury, cadmium, lead and copper in fruiting bodies of edible mushrooms in an emission area of a copper smelter and a mercury smelter.

Four metals were determined by AAS techniques in 56 samples of 23 wild mushroom species collected in a heavily polluted area in eastern Slovakia in 1997 and 1998. The area has been contaminated from historical polymetallic ores mining and smelting and by emissions from a mercury smelter between 1969 and 1993 and from a copper smelter since 1951. No significant differences in metal concentrations (P < 0.05) were found in four species when comparing the periods 1992-1993 and 1997-1998. Considerable contamination of most species was observed mainly for mercury and cadmium. The highest levels of mercury, up to 50 mg kg-1 dry matter, were found in Boletus reticulatus, Lycoperdon perlatum and Marasmius oreades, and of cadmium up to 20 mg kg-1 dry matter in Xerocomus chrysenteron and Lycoperdon perlatum. The latter species also had extremely high lead and copper concentrations in hundreds of milligrams per kilogram dry matter. Concentrations of mercury and copper in caps of four Boletaceae species were significantly (P < 0.05) higher than those in stipes.

Agaricales

Hydroxylating activity of tyrosinase and its dependence on hydrogen peroxide.

The aim of this work was to study the hydroxylation of N, N-dimethyltyramine (DMTA) by tyrosinase in the presence of hydrogen peroxide, a reaction that does not take place without the addition of the hydrogen peroxide. Some properties of this hydroxylating activity are analyzed. The kinetic parameters of mushroom tyrosinase toward hydrogen peroxide (K(m) = 0.5 mM, V(m) = 11 microM/min, V(m)/K(m) = 2.2 x 10(-2) min(-1)) and toward DMTA (K(m) = 0.3 mM, V(m) = 4.8 microM/min, V(m)/K(m) = 16 x 10(-2) min(-1)) were evaluated. There was a lag period, which was similar to the characteristic lag of monophenolase activity at the expense of molecular oxygen. The length of this lag phase decreased with increasing hydrogen peroxide concentration, and disappeared at approximately 0.5 mM H(2)O(2). However, the lag was longer with higher DMTA concentrations. The pH optimum range for this hydroxylating activity was 6.0 to 7.0. The lag also varied with pH, increasing at pH values higher than 6.7. The presence of hydrogen peroxide is necessary for the oxidation of DMTA, as is the presence of active enzyme since the reaction was completely inhibited when selective tyrosinase inhibitors were added.

Agaricales