In vitro incorporation of elongated fatty acyl products into lipid classes in the housefly,Musca domestica L. and the American cockroach,Periplaneta americana (L.) |
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Authors: | Apollo H Vaz Alvin G Wong Ronald C Reitz |
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Affiliation: | (1) Department of Biochemistry, University of Nevada, 89557 Reno, Nevada |
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Abstract: | Thein vitro incorporation of elongated fatty acyl products into various lipid classes was studied in the American cockroach,Periplaneta americana (L.) and the houseflyMusca domestica L. Stearoyl-CoA (18∶0-CoA) and linoleoyl-CoA (18∶2-CoA) were each elongated in microsomal preparations from abdominal epidermal
tissue of the adult cockroach. Incorporation of radioactive tracer into different lipid classes was determined by thin-layer
chromatography (TLC). In the American cockroach, 40–45% of the total radioactive label was incorporated into the free fatty
acid fraction, with smaller amounts in the triglyceride (12–31%) and phospholipid (12–19%) fractions. Of the elongated products
analyzed by radio-high performance liquid chromatography (HPLC), 53–60% was found in the free fatty acid fraction. In the
housefly, the substrates 18∶0-CoA and 18∶1-CoA were used to determine into which lipids the elongated products would become
incorporated. The saturated fatty acyl elongated products were found mainly in the free fatty acid (41%), triglyceride (23%),
and acyl-CoA (17%) fractions. The monounsaturated fatty acyl elongated products were found in the triglyceride (44%), free
fatty acid (11%), acyl-CoA (35%) and phospholipid (10%) fractions in three-day-old males. In three-day-old females, the elongated
products were found in the triglyceride (45%), free fatty acid (28%), acyl-CoA (11%) and phospholipid (15%) fractions. From
these data, it is not possible to determine the identity of the substrate for the conversion of the elongated fatty acyl products
to the corresponding hydrocarbon (Hy). In the cockroach, incubations with 18∶0-CoA and with 18∶2-CoA resulted in small incorporations
into 25∶0 Hy and into 27∶2 Hy, respectively. In the housefly, incubations with 18∶1-CoA resulted in a very small production
of 27∶1 Hy in mature males and 23∶1 Hy in mature female houseflies. These data support the idea that the preparation of subcellular
fractions results in an uncoupling of fatty acid chain elongation from the conversion of the fatty acid to the corresponding
hydrocarbon in both insects. |
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