The regulation of the fatty-acid composition of the triacylglycerols in microsomal preparations from avocado mesocarp and the developing cotyledons of safflower

✍ Scribed by A. K. Stobart; S. Stymne

• Publisher: Springer-Verlag
• Year: 1985
• Tongue: English
• Weight: 742 KB
• Volume: 163
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00395905

✦ Synopsis

The utilisation of [14C]glycerol 3phosphate and [14C]linoleoyl-CoA in the synthesis of triacylglycerol has been studied in the microsomal preparations of developing cotyledons of safflower seed. The results confirm that the glycerol backbone, which flows towards triacylglycerol from phosphatidic acid through the Kennedy pathway, can enter phosphatidylcholine from diacylglycerol. The equilibration between diacylglycerol and phosphatidylcholine offers a mechanism for the return of oleate to phosphatidylcholine for desaturation to linoleate. We have established that the oleate entering position 1 of sn-phosphatidylcholine from diacylglycerol is desaturated in situ to linoleate. The results indicate that the diacylglycerol phosphatidylcholine interconversion coupled to the acyl exchange between acyl-CoA and position 2 of snphosphatidylcholine brings about the continuous enrichment of the glycerol backbone with Clspolyunsaturated fatty acids and hence these enzymes are of major importance in regulating the acyl quality of the accumulating triacylglycerols. Microsomal preparations from avocado mesocarp, however, did not have detectable acyl exchange between acyl-CoA and phosphatidylcholine or diacylglycerol phosphatidylcholine interconversion despite the high activity of the enzymes of the Kennedy pathway. A scheme is presented which incorporates many of the observations on triacylglycerol synthesis and provides a working model for the regulation of acyl quality in linoleate-rich vegetable oils.