Modifying the yeast very long chain fatty acid biosynthetic machinery by the expression of plant 3-ketoacyl CoA synthase isozymes

Eukaryotes express a multi-component fatty acid elongase to produce very long chain fatty acids (VLCFAs), which are building blocks of diverse lipids. Elongation is achieved by cyclical iteration of four reactions, the first of which generates a new carbon-carbon bond, elongating the acyl-chain. This reaction is catalyzed by either ELONGATION DEFECTIVE LIKE (ELO) or 3-ketoacyl-CoA synthase (KCS) enzymes. Whereas plants express both ELO and KCS enzymes, other eukaryotes express only ELOs. We explored the KCS and ELO enzymatic redundancies by expressing the former in yeast strains that lacked endogenous ELO isozymes. Expression of the 26 maize KCS isozymes in wild-type, scelo2 or scelo3 single mutants did not affect VLCFA profiles. However, five of these KCSs were capable of complementing the lethal scelo2; scelo3 double mutant. These rescued strains express novel VLCFA profiles reflecting the different catalytic capabilities of the KCS isozymes. These novel strains offer a platform to explore the relationship between VLCFA profiles and cellular physiology.

Seasonal variations in the component fatty acid distributions of the lipids of Balanus balanoides

A study has been made of the seasonal variations in the component acids of the lipid fractions of Balanus balanoides. The relative proportions of the polyenoic acids in the triglycerides drop sharply during the winter. They reach a minimum in the early spring and then gradually rise to a maximum in the late autumn. These changes are largely balanced by increases in the saturated acids, principally 16:0 and 18 :o.1 During the winter there is a marked decrease in the triglyceride to phospholipid ratio as the depot fats are mobilised as food reserves. The proportions of the polyethenoid acids in the phospholipids decline slowly during the winter and spring and attain their minimum in June-July. This fall is mainly counterbalanced by increases in the amounts of saturated acids, principally 14:0 and 16:0. It seems likely that the observed decreases in the polyenoic acids are brought about by selective utilization of these compounds as reserves during the winter when food is scarce and depot lipid has been depleted.

The component fatty acids of the lipids of some species of marine and freshwater molluscs

The component fatty-acid patterns of the triglycerides, phospholipids and, in some instances, sterol esters of a number of aquatic molluscs have been determined. The species examined include several of marine origin (Chlamys opercularis, Crepidula fornicata, Mytilus edulis, Neptunea antiqua, Patella vulgata and Pecten maximus) and one of freshwater origin (Anodonta sp.). The marine species contained considerable proportions of highly unsaturated acids of the C and C series (eg. 20:5 and 22:5) which are characteristic of the lipids of most aquatic plants and animals. In general, the relative percentages of 18:1,20:1 and 20:4 (5,8,11,14) were greater in the lipids of the marine gastro-pods than in those of the pelecypods. The differences between the fatty-acid distributions of the Anodonta sp. and marine members of the pelecypoda are analogous to those existing between other freshwater and marine animals. Studies were made of the seasonal variations in the relative proportions and fatty-acid compositions of the triglycerides and phospholipids in P. vulgata. The relative proportions of 20:4 (5,8,11,14) and 20:5 in the triglycerides rose abruptly from minimum values in January to maximum values in March and thereafter declined slowly. These changes were mainly compensated by inverse variations in the proportions of saturated and oleic acids. In contrast to the triglycerides there appears to be no significant seasonal differences in the fatty acid patterns of the phospholipids.

The Effect of diet on the Component Fatty-Acid Composition of Artemia Salina

Artemia salina has been reared on unialgal diets of Phaeodactylum tricornutum, Monochrysis lutheri, Platymonas tetrahele and Chlamydomonas sp. In most instances the component fatty-acid distribution of the Artemia bore little resemblance to that of its food. Thus, oleic and stearic acids are relatively enriched in the shrimps, whereas hexadecatetraenoic acid is much depleted. It is suggested that the metabolic requirements of the shrimps is of at least equal importance to the composition of their food in determining the component fatty-acid distribution of their lipids.

Component Fatty Acids of the Total Lipids of Some Marine Phytoplankton

A range of 27 marine phytoplankton species, representative of several of the principal classes, has been grown under similar conditions in Erd-Schreiber medium with abundant nutrients. Harvesting was carried out 20 days after inoculation while vigorous growth was proceeding. The component fatty acids of the lipids extractable with chloroform-methanol were determined by gas-liquid chromatography. In all, 40 fatty acids were determined. It is likely that the component fatty-acid distribution may be valuable for taxonomic purposes. Thus, specific fatty-acid assemblages may characterize particular Phyla or even classes. For example, the Bacillariophyceae are differentiated from the other organisms examined by the virtual absence of 18:2, 18:3 and 1814; the Cryptophyta are distinguished by their high content of 20:1. The fatty-acid arrays of species belonging to the same genus are frequently very similar, e.g. Dunaliella primolecta and D. tertiolecta.