Enzymic preparation of dioxygen-18 labelled leukotriene E4 and its use in quantitative gas chromatography—mass spectrometry

A simple and rapid method is described for the preparation of a stable isotope oxygen-18 labelled leukotriene E₄ (LTE₄). Oxygen-18 labelling of LTE₄ methyl ester in oxygen-18 water catalysed by a pig liver esterase resulted in the incorporation of two oxygen-18 atoms in the carboxylic group of LTE₄ to the extent of 89.8% ([¹⁸O₂]LTE₄) and one oxygen-18 atom to the extent of 9.4% ([¹⁶O¹⁸O]LTE₄), with only 0.7% remaining unchanged ([¹⁶O₂]LTE₄). [¹⁸O₂]LTE₄ was found not to back-exchange following incubation in acidified urine (pH 4.0) at 4°C for up to 20 h. [¹⁸O₂]LTE₄ was demonstrated to be a useful internal standard in a method for the quantitative determination of LTE₄ in human urine involving high-performance liquid chromatography and gas chromatography with negative-ion chemical ionization tandem mass spectrometry: the concentration of LTE₄ in a 24-h urine sample of a healthy subject was determined to be 68.1 pg/ml.     

Thermal Denaturation of Native Striatal Tyrosine Hydroxylase: Increased Thermolability of the Phosphorylated Form of the Enzyme

Tyrosine hydroxylase was purified from bovine corpus striatum. The native enzyme had a half-life of 15 +/- 3 min at 50 degrees C. Phosphorylation of tyrosine hydroxylase with protein kinase purified from both corpus striatum and heart activated the enzyme, but activity was rapidly lost with additional preincubation of the enzyme at 30 degrees C. Thermal denaturation studies indicated that phosphorylated tyrosine hydroxylase had a half-life of 5 +/- 2 min at 50 degrees C     

Genetic variability of proteins from plasma membranes and cytosols of mouse organs

The genetic variability of membrane proteins (structure-bound proteins) and cytosol proteins (water-soluble proteins) was investigated in two inbred strains of the mouse, C57BL/6J and DBA/2J. Membrane proteins and cytosol were isolated from the brain and liver of the mouse. The proteins were separated by two-dimensional electrophoresis. A high number of genetic variant proteins (brain, 30; liver, 72) was found in the cytosol. Most of these variants represented changes in the amount of proteins. Electrophoretic mobility changes occurred only in about 1% (brain, 6; liver, 9) of all protein spots of a two-dimensional pattern. In contrast to the cytosol proteins, no genetic variation was detected among the membrane proteins, not even for the quantitative characteristics of the protein spots. The results obtained for the two classes of proteins suggest that the degree of variability in the amount of proteins is related to the degree of variability in the structure of proteins.     

Synthesis of specifically deuterated saturated and unsaturated phosphatidylserines

A facile chemical synthesis of 1,2-dioleoyl and 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine as well as the synthesis of several deuterated derivatives of phosphatidylserine (2 and 3 positions of serine and in the 3-glycerol position) are described. 360 MHz ¹H NMR spectra of phosphatidylserine and the optical activity of various phosphatidylserine diastereomers were measured.     

β-Ionon und patchoulialkohol aus den unterirdischen teilen von Valeriana officinalis

l-(+)-Bornesitol was detected in 23 of 33 genera of Gentianaceae investigated. The only subtribe without l-(+)-bornesitol (3 species tested) was Exacinae. None of the five genera of Menyanthaceae examined were found to contain l-(+)-bornesitol.     

A novel reaction of S-adenosyl-L-methionine correlated with the activation of pyruvate formate-lyase

Conversion of the inactive form of pyruvate formate-lyase to the catalytically active enzyme is accomplished by the Fe-dependent ‘enzyme II’; reduced flavodoxin, S-adenosyl-L-methionine and the effector pyruvate are required. It was found that adenosylmethionine is reductively processed during activation of pyruvate formate-lyase to yield methionine, adenine and 5-deoxyribose. We suggest that transient adenosylation of enzyme II is required for its function as a converter enzyme.     

Die cucurbitacine in Bryonia alba und Bryonia dioica

The cucurbitacins in roots of Bryonia dioica and B. alba have been investigated. Both species contain the cucurbitacins E, B, I, D, J, K and L, the dihydrocucurbitacins E and B, and tetrahydrocucurbitacin I. The detection of certain cucurbitacin aglycones depends upon the date of harvest, the duration of storage and the methods used for extraction.