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F W Hemming

Publications and source records attributed to F W Hemming.

At least 73 records · Page 4Linked to original sources
PubMed1972

The transfer of mannose from guanosine diphosphate mannose to dolichol phosphate and protein by pig liver endoplasmic reticulum.

When pig liver microsomal preparations were incubated with GDP-[(14)C]mannose, 10-40% of the (14)C was transferred to mannolipid and 1-3% to mannoprotein. The transfer to mannolipid was readily reversible and GDP was one of the products of the reaction. It was possible to reverse the reaction by adding excess of GDP and to show the incorporation of [(14)C]GDP into GDP-mannose. When excess of unlabelled GDP-mannose was added to a partially completed incubation there was a rapid transfer back of [(14)C]mannose from the mannolipid to GDP-mannose. The other product of the reaction, the mannolipid, had the properties of a prenol phosphate mannose. This was illustrated by its lability to dilute acid but stability to dilute alkali, and by its chromatographic properties. Dolichol phosphate stimulated the incorporation of [(14)C]mannose into both mannolipid and into protein, although the former effect was larger and more consistent than the latter. The incorporation of exogenous [(3)H]dolichol phosphate into the mannolipid, and its release, accompanied by mannose, on treatment of the mannolipid with dilute acid, confirmed that exogenous dolichol phosphate can act as an acceptor of mannose in this system. It was shown that other exogenous polyprenol phosphates (but not farnesol phosphate or cetyl phosphate) can substitute for dolichol phosphate in this respect but that they are much less efficient than dolichol phosphate in stimulating the transfer of mannose to protein. Since pig liver contained substances with the chromatographic properties of both dolichol phosphate and dolichol phosphate mannose, which caused an increase in transfer of [(14)C]mannose from GDP-[(14)C]mannose to mannolipid, it was concluded that endogenous dolichol phosphate acts as an acceptor of mannose in the microsomal preparation. The results indicate that the mannolipid is an intermediate in the transfer of mannose from GDP-mannose to protein. Some 4% of the mannose of a sample of mannolipid added to an incubation was transferred to protein. A scheme is proposed to explain the variations with time in the production of radioactive mannolipid, mannoprotein, mannose 1-phosphate and mannose from GDP-[(14)C]mannose that takes account of the above observations. ATP, ADP, UTP, GDP, ADP-glucose and UDP-glucose markedly inhibited the transfer of mannose to the mannolipid.

Animals↗
PubMed1970

The stereochemistry of betulaprenol biosynthesis.

By using stereospecifically double-labelled radioactive mevalonates it was shown that betulaprenols-6 to -9, found in the woody tissue of Betula verrucosa, each contain three biogenetically trans-isoprene residues and that the remaining residues are biogenetically cis. The results obtained with these radioactive mevalonates also indicated that the activity of isopentenyl pyrophosphate isomerase is low relative to the activity of prenyltransferase in this woody tissue. The incorporation of radioactive farnesyl pyrophosphate and radioactive geranylnerol and the lack of incorporation of radioactive geranylgeraniol into betulaprenols-6 to -9 demonstrated that they are formed by the cis-additions of isoprene residues to all-trans-farnesyl pyrophosphate.

Alcohols↗
PubMed1970

The characterization and stereochemistry of biosynthesis of dolichols in rat liver.

It was shown that rat liver contains a series of dolichols with chain lengths of from 17 (or possibly 16) to 21 isoprene residues, the main constituent of the mixture being dolichol-18. By using double-labelled radioactive mevalonates it was demonstrated that each of these dolichols possesses three biogenetically trans-isoprene residues and that the remaining residues are biogenetically cis, suggesting that these polyprenols are biosynthesized from all-trans-farnesyl pyrophosphate by the cis additions of isoprene residues, followed by saturation of the alpha-isoprene residue. The results obtained with these radioactive mevalonates also indicated that the activity of isopentenylpyrophosphate isomerase is low relative to the activity of prenyltransferase in rat liver.

Alcohols↗
PubMed1970

The characterization of undecaprenol of Lactobacillus plantarum.

Evidence for the presence of undecaprenol in the unsaponifiable lipid of Lactobacillus plantarum (N.C.I.B. 6376) is presented. Characterization of the compound was based mainly on mass, i.r. and n.m.r. spectrometry. The prenol was isolated at a concentration of 40mug/g wet wt. of bacteria and contained over 90% (1.0-5.4% of the dose) of the (14)C present in the unsaponifiable lipid after incubation of the bacteria with [2-(14)C]mevalonate. N.m.r. spectrometry indicated the presence of two internal trans-, one alpha-cis- and seven internal cis-isoprene residues per molecule. The (3)H/(14)C ratios of the prenol after incubation of the bacteria with [2-(14)C,(4R)-4-(3)H(1)]- and [2-(14)C,(4S)-4-(3)H(1)]-mevalonate were in agreement with this stereochemistry. There was no evidence of saturated isoprene residues in the molecule. The undecaprenol appeared to be accompanied by much smaller quantities of decaprenol and nonaprenol.

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PubMed1970

Polyprenols.

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Alcohols↗
PubMed1969

Polyprenols.

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Alkenes↗
PubMed1968

The characterization and distribution of hexahydropolyprenyl esters in cultures of Aspergillus fumigatus Fresenius.

The total mycelial lipid of Aspergillus fumigatus was analysed and over half of its hexahydropolyprenol was shown to be esterified with fatty acids. Comparison of the fatty acid content of the prenyl esters with the sterol ester and the total lipid indicated a marked predominance of saturated fatty acids in the polyprenyl esters. The predominant acids esterified to the prenols were palmitic acid, linoleic acid, oleic acid, lignoceric acid, stearic acid and palmitoleic acid. Most of the unesterified polyprenol was found in the mitochondrial fraction, but the esterified prenol was equally distributed throughout the cell fractions. This distribution was unlike that found for ergosteryl ester in the same tissue.

Alcohols↗
PubMed1967

The characterization and properties of castaprenol-11, -12 and -13 from the leaves of Aesculus hippocastanum (horse chestnut).

The isolation and purification of a mixture of cis-trans-polyprenols from the leaves of Aesculus hippocastanum (horse chestnut) are described. Results of studies involving mass spectrometry, nuclear magnetic resonance, infrared spectroscopy, micro-hydrogenation and ozonolytic degradation show the mixture to be made up of undecaprenol, dodecaprenol and tridecaprenol with dodecaprenol predominating. Each of the prenols contains three trans internal isoprene residues and a cis ;OH-terminal' isoprene residue. They differ from each other only in the number of cis internal isoprene residues. The trivial names castaprenol-11, castaprenol-12 and castaprenol-13 are proposed to describe these compounds. Gas-liquid-chromatographic and reversed-phase partition thin-layer chromatographic evidence suggest the presence in the mixture of small quantities of castaprenol-10 also.

Acetates↗
PubMed1967

The characterization of ficaprenol-10, -11 and 12 from the leaves of Ficus elastica (decorative rubber plant).

Evidence from mass, nuclear-magnetic-resonance and infrared spectrometry and from gas-liquid and thin-layer chromatography is presented in favour of the presence of cis-trans-decaprenol, -undecaprenol and -dodecaprenol in the mixture of polyprenols (2.6mg./g.) isolated from leaf tissue of Ficus elastica. The trivial names ficaprenol-10, -11 and -12 are proposed. Nuclear-magnetic-resonance studies showed that each of these prenols contains three trans internal isoprene residues and a cis ;OH-terminal' isoprene residue. Ficaprenol-11 is the major component of the mixture. Chromatographic evidence suggests the presence also of small amounts of ficaprenol-9 and -13. The precise position of the three trans internal isoprene residues was not determined but it is suggested that these are adjacent to the omega-terminal isoprene residue and that the ficaprenols are formed from all-trans-geranylgeranyl pyrophosphate. It is also suggested that ficaprenol-10, -11, -12 and -13 are probably the same compounds as castaprenol-10, -11, -12 and -13.

Alcohols↗
PubMed1967

Characterization of the hexahydropolyprenols of Aspergillus fumigatus Fresenius.

The isolation and properties of a group of alcohols from the mycelium of Aspergillus fumigatus Fresenius are described. Mass-, nuclear-magnetic-resonance- and infrared-spectrometric studies coupled with evidence from ozonolytic degradation and chromatography show the mixture to contain hexahydroprenols-18, -19, -20, -21, -22, -23 and -24. Each contains a saturated ;hydroxy-terminal' isoprene residue, a saturated omega-terminal isoprene residue and a saturated zeta-isoprene residue (adjacent to the omega-residue). The presence of only two trans-isoprene residues is also a feature of the series of alcohols, but the precise position of these in each molecule is not known.

Alcohols↗
PubMed1967

The stereochemistry of hexahydroprenol, ubiquinone and ergosterol biosynthesis in the mycelium of Aspergillus fumigatus Fresenius.

1. The mycelium of Aspergillus fumigatus has been shown to incorporate mevalonate into squalene, ubiquinone, ergosterol and hexahydroprenol. 2. The (3)H/(14)C ratio in ubiquinone, biosynthesized from [2-(14)C-(4R)-4-(3)H(1)]mevalonate, is the same as in the squalene; essentially no (3)H was incorporated from [2-(14)C-(4S)-4-(3)H(1)]mevalonate, indicating the biosynthesis of biogenetically trans-isoprene units. 3. The (3)H/(14)C ratio for ergosterol (from ;4R-mevalonate') was 3:5, showing that the proton at C-24 is not lost during alkylation of the side chain; it probably migrates to C-25. 4. As (3)H from both mevalonates was incorporated into the hexahydroprenols the biosynthesis of both cis- and trans-isoprene units must occur. 5. The saturated omega- and psi-isoprene units are shown to be biogenetically trans, as are two of the unsaturated residues. 6. The saturated alpha- and unsaturated beta-isoprene residues are both biogenetically cis. 7. An inexplicable loss of approximately half of the olefinic protons from the cis-portion of hexahydroprenol occurs; possible reasons for this loss are discussed. 8. Increase in chain length of the hexahydroprenols is by a cis addition. 9. A biosynthesis of hexahydroprenols by addition of cis-isoprene units to all-trans-geranylgeranyl pyrophosphate, or a dihydro or tetrahydro derivative thereof, is suggested.

Alcohols↗
PubMed1967

The subcellular distribution and biosynthesis of castaprenols and plastoquinone in the leaves of Aesculus hippocastanum.

Intact chloroplasts and cell walls were prepared from horse-chestnut leaves that had previously metabolized [2-(14)C]mevalonate. The bulk of the castaprenols and plastoquinone-9 was found within the chloroplasts. The remaining portion of the castaprenols was associated with the cell-wall preparation whereas that of the plastoquinone-9 was probably localized in the soluble fraction of the plant cell. The (14)C content of these compounds of different cell fractions indicated the presence of polyisoprenoid-synthesizing activity both inside and outside the chloroplasts. This was confirmed by the relative incorporation of (14)C when ultrasonically treated and intact chloroplasts were incubated with [2-(14)C]mevalonate. As the leaves aged (on the tree) an increase in extraplastidic castaprenols and plastoquinone-9, together with associated synthesizing activities, was observed.

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