Showing papers by "John L. Harwood published in 1989"

Lipid metabolism in algae.

Abstract: Publisher Summary The lipid composition and metabolism of algae are exceptionally varied This chapter focuses on groups of organisms (algae) that have been studied in reasonable detail To lay a basis for further discussion of metabolism, the lipid structure and occurrence in algae is discussed The metabolic sections then deal with organisms of increasing complexity, from the primitive cyanobacteria to marine macroalgae Finally, the chapter ends with a discussion on green algae, which can be regarded as the nearest in metabolic characteristics to higher plants

Acyl lipid metabolism in the oleaginous yeastRhodotorula gracilis (CBS 3043)

Abstract: The effects of culture conditions on acyl lipid metabolism in the oleaginous yeastRhodotorula gracilis (CBS 3043) have been investigated. Growth ofR. gracilis under conditions of nitrogen-limitation resulted in the accumulation of large quantities of triacylglycerols. Thin layer and gas chromatographic analysis of total lipid extracts revealed that the majority of this storage lipid was produced by stationary-phase cells. In contrast, no such increase in triacylglycerol biosynthesis could be detected in carbon-limited cells. Freeze-fracture electron microscopy evidence supported these findings. Growth medium composition was found to have little effect on the relative abundance of the primary phospholipid classes present inR. gracilis. The acyl compositions of triacylglycerols were similarly unchanged by alterations in the composition of the growth medium. In contrast, the degree of unsaturation exhibited by the phospholipid fractions appeared to be particularly sensitive to this external parameter. Acyl quality of triacylglycerol pools extracted from nitrogen-limited cells were observed to become increasingly saturated as cultures increased in age. Growth of nitrogen-limited cells at a lower growth temperature was observed to have little effect on triacylglycerol accumulation. However, both triacylglycerol and phospholipid fractions extracted from these cultures were found to contain increased proportions of the polyunsaturated fatty acid, α-linolenate.

Changes in phospholipid fatty acid composition and triacylglycerol content in mouse tissues after infection with bacille Calmette-Guérin.

Abstract: Changes in the lipids of tissues from mice infected with bacille Calmette-Guerin (BCG) have been detected by gas-liquid chromatography. Infection with BCG resulted in (1) an increase in the polyunsaturated to saturated fatty acid ratio of phospholipids and (2) a decrease in the total triacylglycerol fatty acid content of spleen, liver and peritoneal macrophages. The alteration in fatty acid composition was significant in the phosphatidylethanolamine fraction of the phospholipids. The relation of these findings to an increased sensitivity to bacterial endotoxins is discussed.

Solubilization and studies of cereal lipases

Abstract: accumulation. The induction of b-ketoacyl-ACP synthase 1 and 11 is similar to that of ACP (Slabas et ul., 1987) and enoyl-ACP reductase (Slabas et ul., 1986) from oilseed rape. In contrast, oilseed rape acetyl-CoA carboxylase shows a rapid loss of activity after fatty acid accumulation is complete (Turnham & Northcote, 1984). Details of a typical purification of P-ketoacyl-ACP synthase 1 from oilseed rape are given in Table 1. The key to the successful purification of P-ketoacyl-ACP synthase I was the use of f.p.1.c. Mono Q ion-exchange chromatography at pH 7.5 and pH 9.0. From 8500 mg of starting protein we were able to obtain 8 pg of homogeneous P-ketoacyl-ACP synthase 1. The low recovery of enzyme activity is an indication of the instability of P-ketoacyl-ACP synthase 1 during purification. The purified enzyme was also very unstable. The native M, values of P-ketoacyl-ACP synthase I and 11 were determined by gel filtration chromatography. The average hi', value of P-ketoacyl-ACP synthase I was 86 700 and for P-ketoacyl-ACP synthase 11 the average M , value was determined to be 87800. The subunit M, value of P-ketoacyl-ACP synthase 1 determined by SDS/polyacrylamide-gel electrophoresis was 43 000, suggesting that the enzyme is a homodimer. The native values reported here are very similar to those obtained for the P-ketoacyl-ACP synthase I and 11 from E. coli, i t . 80 000 and 85 000, respectively (Garwin et ul., 1980). The E. coli enzymes are also homodimeric. P-Ketoacyl-ACP synthase I co-purified with synthase I1 through ammonium sulphate fractionation and hydroxyapatite chromatography and the enzymes were only partially separated by gel filtration chromatography. However, the enzymes could be separated almost completely by f.p.1.c. Mono Q ion-exchange chromatography. Thus, we have been able to show that the two activities reside in different proteins.