Omega 3 and omega 6 fatty acids in human and animal health: an African perspective.

Lipids are essential for plant and animal development, growth and nutrition and play critical roles in health and reproduction. The dramatic increase in the human population has put increasing pressure on human food sources, especially of those sources of food which contain adequate levels of polyunsaturated fatty acids (PUFAs) and more importantly, sources of food which have favorable ratios of the n-3 (18-carbon, α-linolenic acid, ALA) to n-6 (18-carbon linoleic acid, LA) PUFAs. Recent studies have demonstrated the beneficial effects of the n-3 PUFAs in diets as well as potentially negative effects of excessive levels of n-6 PUFAs in diets. This review discusses these human health issues relating to changes in diets based on environmental and industrial changes as well as strategies in East Africa for improving lipid composition of food using indigenous sources.

Effects of dietary flax seed and sunflower seed supplementation on normal canine serum polyunsaturated fatty acids and skin and hair coat condition scores.

This prospective study involved supplementing 18 normal dogs with flax seed (FLX) and sunflower seed (SUN) and evaluating their effects on skin and hair coat condition scores and serum polyunsaturated fatty acids (PUFA) concentrations. Skin and hair coat were evaluated in a double-blinded fashion using a numeric scoring system and serum PUFA concentrations were determined. Our hypothesis was that changes in serum PUFA concentrations are associated with improvements in skin and hair coat and that serum PUFA would provide an objective method for making dietary fatty acid supplement recommendations. Although a numerical improvement was found in hair coat quality in both groups, this improvement was not sustained beyond 28 days. The relative per cent of 18:3n-3 concentrations in serum phospholipids increased in the FLX treated dogs but these concentrations remained unchanged in the SUN treated dogs. Also, elevations in relative per cent of 18:2n-6 concentrations in serum phospholipids were seen in the FLX group. The ratio of serum polyunsaturated to saturated fatty acids also showed a transient increase. These increases preceded the peak skin condition score peak value by approximately 14 days. It was concluded that a 1-month supplementation with either flax seed or sunflower seed in dogs provides temporary improvement in skin and hair coat. These changes appeared to be associated with increased serum 18 carbon PUFA.

The covalent attachment of polyamines to proteins in plant mitochondria.

Plant mitochondria from both potato and mung bean incorporated radioactivity into acid insoluble material when incubated with labelled polyamines (spermine, spermidine and putrescine). Extensive washing of mitochondrial precipitates with trichloroacetic acid and the excess of cold polyamine failed to remove bound radioactivity. Addition of nonradioactive polyamine stopped further incorporation of radioactivity but did not release radioactivity already bound. The radioactivity is incorporated into the membrane fraction. The labelling process has all the features of an enzymatic reaction: it is long lasting with distinctive kinetics peculiar to each polyamine, it is temperature dependent and is affected by N-ethylmaleimide. The latter inhibits the incorporation of putrescine but stimulates the incorporation of spermine and spermidine. Treatment of prelabelled mitochondria with pepsin releases bound radioactivity thus indicating protein to be the ligand for the attachment of polyamines. HPLC of mitochondrial hydrolysates revealed that the radioactivity bound to mitochondria is polyamines; traces of acetyl polyamines were also found in some samples. On autoradiograms of SDS/PAGE gels several radioactive bands of proteins were detected. Protein sequencing of labelled spots from a 2D gel gave a sequence which was 60% identical to catalase. We suggest that the attachment of polyamines to mitochondrial proteins occurs cotranslationally possibly via transglutaminases.

The characterisation of the shikimate pathway enzyme dehydroquinase from Pisum sativum.

Peptides accounting for 157 residues of the bifunctional shikimate pathway enzyme, dehydroquinase/shikimate dehydrogenase, of Pisum sativum were sequenced. Three of the peptides were homologous to regions in Escherichia coli dehydroquinase and two to E. coli shikimate dehydrogenase. The pea dehydroquinase activity was inhibited by treatment with dehydroquinate plus sodium borohydride, establishing it as a type I dehydroquinase. Synthetic oligonucleotides designed from the amino acid sequence were used as PCR primers to amplify fragments of P. sativum cDNA. DNA sequence analysis showed that these amplified products were derived from dehydroquinase/shikimate dehydrogenase cDNA. The complete amino acid sequence of the dehydroquinase domain has been defined; it is homologous to all other type I dehydroquinases and is N-terminal.

The purification and properties of ferredoxin-NADP(+)-oxidoreductase from roots of Pisum sativum L.

A ferredoxin-NADP(+)-oxidoreductase (FNR) was purified to homogeneity from pea root plastids to a specific activity of 200 nkat.mg protein-1, following acetone precipitation and ferredoxin affinity chromatography. The molecular weight of the enzyme was estimated to be 36,000 and 33,800 by SDS-polyacrylamide gel electrophoresis and molecular exclusion chromatography, respectively. The absorption spectrum of the enzyme suggests it contains flavin as a prosthetic group. The enzyme requires NADPH and did not use NADH as an electron donor. The Km values for NADPH and ferredoxin were calculated to be 28 and 5 microM, respectively. The enzyme exhibited optimal activity at pH 8.0. Although resembling the leaf enzyme in most properties, amino terminal sequencing demonstrates clear differences between the leaf and root proteins and suggests closer homology of the pea root enzyme with the enzyme from spinach roots. A polyclonal antibody against the pea root plastid enzyme was raised by the immunization of rabbits. Judging by immunodiffusion only partial identity was observed between the root plastid and chloroplast FNR. The root plastid FNR enzyme activity was precipitated with increasing concentrations of the antibody, in contrast to the chloroplast enzyme which was not inhibited. The potential usefulness of these antibodies is discussed.

Identification and characterization of a GroEL homologue in Rhodobacter sphaeroides.

A protein closely related to the Escherichia coli GroEL protein has been isolated from Rhodobacter sphaeroides. Native and SDS-polyacrylamide gel electrophoresis of this protein have shown that it is present in the cell as a multimeric complex of Mr 670,000 which is composed of a monomer of Mr 58,000. Antisera raised against the Mr 58,000 polypeptide have been shown to cross-react with GroEL and the alpha subunit of the pea plastid chaperonin. The N-terminal amino acid sequence of the Mr 58,000 polypeptide is identical to that of GroEL at 15 of 19 residues and is also closely related to the alpha subunit of the pea plastid chaperonin, though less so to the beta subunit.

Plant mitochondrial F1-ATPase. The presence of oligomycin-sensitivity-conferring protein (OSCP).

Purified pea (Pisum sativum) cotyledon F1-ATPase contains six subunits rather than the five usually reported for F1-ATPases. The additional 26.5 kDa (delta) subunit is shown by immunoblotting and N-terminal amino acid sequencing to be similar to bovine oligomycin-sensitivity-conferring protein (OSCP). It is concluded that the delta subunit of plant mitochondrial F1-ATPase is the plant OSCP. This OSCP subunit occurs in all mono- and di-cotyledonous species of plants tested (maize, oats, peas, potatoes, sweet potatoes and turnips).