Enzymatic systems that synthesize and degrade glycerolipids possessing ether bonds

Terminal steps in pheromone biosynthesis byHeliothis virescens andH. zea

In vivo application to the sex pheromone gland ofHeliothis Virescens andH. Zea of large quantities of alcohols normally present in small amounts resulted in the preferential conversion of the alcohols to the corresponding pheromonal aldehydes. Amounts of the minor component aldehydes were increased up to 15-fold by selectively applying large quantities of the alcohol precursors. Using this technique, we have inducedH. virescens to convert "bombykol," the sex pheromone of the silkworm, to the corresponding aldehyde, "bombykal," and have induced femaleH. zea to produce the same sex pheromone components used byH. virescens by applying tetradecanol and (Z)-9-tetradecenol to the surface of the gland. Further, treatedH. zea females were attractive toH. virescens males and caused males to attempt interspecific copulation repeatedly. We have also found that the enyzme involved in this conversion is dependent on the presence of molecular oxygen, indicating that a nonspecific alcohol oxidase is responsible for the terminal biosynthetic step in pheromone production by bothH. virescens andH. zea.

Chemical and behavioral analyses of volatile sex pheromone components released by callingHeliothis virescens (F.) females (Lepidoptera: Noctuidae)

Gas chromatographic and mass spectral analyses were conducted on pheromone gland extracts, volatiles collected from excised pheromone glands, and volatiles collected from calling females. In addition to tetradecanal, (Z)-9-tetradecenal, hexadecanal, (Z)-7-hexadecenal, (Z)-9-hexadecenal, and (Z)-11-hexadecenal, four other compounds, tetradecanol, (Z)-9-tetradecenol, hexadecanol, and (Z)-11-hexadecenol, were also identified from gland extracts. Only the six aldehyde components were found in gland and female volatile collections. The mean percentage of components identified from volatiles collected from calling females was 13.0% tetradecanal, 18.1% (Z)-9-tetradecenal, 7.3% hexadecanal, 0.6% (Z)-7-hexadecenal, 1.0% (Z)-9-hexadecenal, and 60.0% (Z)-11-hexadecenal. Bioassays using rubber septa formulated to release the female volatile blend indicated that all six aldehyde components play major roles in close-range male reproductive behavior. Deletion of (Z)-9-hexadecenal from the six-component blend reduced the number of copulation attempts while (Z)-7-hexadecenal exerted subtle effects on all close range behaviors. Tetradecanal affected the number of times males reorient from close range. Deletion of hexadecanal from the six-component blend resulted in a significant reduction in the number of times males landed. Comparison of the six-component synthetic blend (released at somewhat less than 1 female equivalent per hour) with calling females indicated that the six-component blend was indistinguishable from the females in inducing all of the behaviors monitored.

Enzymatic reduction of fatty acids and acyl-CoAs to long chain aldehydes and alcohols

The properties of enzymatic systems involved in the synthesis of long chain aldehydes and alcohols have been reviewed. Fatty acid and acyl-CoA reductases are widely distributed and generate fatty alcohols for ether lipid and wax ester synthesis as well as fatty aldehydes for bacterial bioluminescence. Fatty alcohol is generally the major product of fatty acid reduction in crude or membrane systems, although reductases which release fatty aldehydes as products have also been purified. The reduction of fatty acid proceeds through the ATP-dependent formation of acyl intermediates such as acyl-CoA and acyl protein, followed by reduction to aldehyde and alcohol with NAD(P)H. In most cases, both the rate of fatty acid conversion and acyl chain specificity of the reaction are determined at the level of reduction of the intermediate. The reduction of fatty acids represents the major pathway for the control of the synthesis of fatty aldehydes and alcohols. Several other enzymatic reactions involved in lipid degradation also release fatty aldehydes but do not appear to play an important role in long chain alcohol synthesis.

Metabolism of 1-0-[1'-14C]octadecyl-sn-glycerol in Leishmania donovani promastigotes. Ether lipid synthesis and degradation of the ether bond

A long-chain 0-alkylglycerol, 1-0-[1'-14C]octadecyl-sn-glycerol, was taken up and metabolized extensively in Leishmania donovani promastigotes grown on a lipid-free, semi-defined medium as well as on a lipid-free, synthetic medium in nearly identical ways. Cleavage of the ether bond was the main event even after short incubation times (1 h) and low precursor concentration (2 microM), as judged from the appearance of radioactive acyl moieties residing mainly in phosphatidylcholine. In addition, labeled plasmanyl inositol and plasmenyl ethanolamine were formed to a considerable extent. However, when administered in higher concentrations (25 microM), 1-0-alkyl-sn-glycerols as well as their enantiomers inhibited lipid metabolism dramatically, accompanied by rounding of the cells and appearance of cellular debris in the medium. This effect was not dependent on the aliphatic side chain (12:0, 16:0, 18:0, 18:1) of the 0-alkylglycerols. It is suggested that, by incorporation into cellular membranes, 0-alklglycerols affect factors responsible for the interaction of membranes and the cytoskeleton as well as enzymes of lipid metabolism.

The dynamics of membrane structure

The membranes of living organisms are involved in many aspects of the life, growth and development of all cells. The predominant structural elements of these membranes are lipids and proteins and the basic strucvture of these molecules has been reviewed. The physical properties of the lipid constituents particularly their behavior in aqueous systems has led to the concepts of thermotropic and lyotropic mesomorphism; the interaction between different types of lipid molecules modulate this behavior. Interaction of phospholipids in aqueous systems with cholesterol, ions and drugs have been examined in this context. In addition a variety of model lipid-protein systems have been investigated and the implications of interactions between lipids and different proteins in biological membranes has been evaluated. This leads to a detailed consideration of the way lipids and proteins ae organized in cell membranes and contains an appraisal of the evidence supporting contemporary views of membrane structure. Particular attention has been devoted to the question of how mobile the components are within the structure. Particular attention has been devoted to the question of how mobile the components are within the structure. Finally the biosynthesis, turnover and modulation of the properties of interacting membrane constituents is critically reviewed and possible ways of controlling the behavior of cells and organisms by altering the structural parameters of different membranes has been considered.

Composition of O-alkyl and O-alk-1-enyl moieties in the glycerolipids of the human adrenal

A comparison of human adult and fetal adrenals with respect to their levels of glyceryl ether lipids and other lipid components is reported. Fetal glands contained significantly lower levels of alk-1-enyl phosphoglycerides and of cholesterol. Neutral glyceryl ether diesters, and ethanolamine and choline phosphoglycerides were isolated from adult adrenal tissue. The composition of the O-alkyl glycerol groups in these lipid fractions was obtained by means of gas chromatography of the trimethylsilyl ethers and diacetyl derivatives; O-alk-1-enyl glycerols were analyzed as their diacetates. About one-half of the alkyl and alk-1-enyl glycerol moieties present in glyceryl ether diesters contained hydrocarbon side chains with 20, 22, or 24 carbon atoms. Long hydrocarbon chains (C19-24) were also found in the O-alkyl glycerol moieties present in the total lipids of fetal adrenals.

The age-related occurrence of wax esters in the mouse preputial gland tumour

The mouse preputial gland tumour (ESR-586) accumulates wax esters from between 20 and 25 days after transplantation until they become the most abundant lipid class. Prior to this time wax esters are not detectable. The process occurs in both male and female host mice and appears to be determined by a response of the host to the tumour, rather than by a property of the tumour itself. The most abundant fatty alcohol present in the wax esters is hexadecanol. This contrasts with the greater proportions of the C20 to C24 chains found for the alkyl portion of the alkyldiacylglycerols, for which the precursors are fatty alcohols.