The biosynthesis and nutritional uses of carotenoids.

Incorporation of 13C-labelled glucose, acetate, pyruvate or erythrose allowed the determination of the origin of the carbon atoms of triterpenoids of the hopane series and/or of the ubiquinones from several bacteria (Zymomonas mobilis, Methylobacterium fujisawaense, Escherichia coli and Alicyclobacillus acidoterrestris) confirmed our earlier results obtained by incorporation of 13C-labelled acetate into the hopanoids of other bacteria and led to the identification of a novel biosynthetic route for the early steps of isoprenoid biosynthesis. The C5 framework of isoprenic units results most probably (i) from the condensation of a C2 unit derived from pyruvate decarboxylation (e.g. thiamine-activated acetaldehyde) on the C-2 carbonyl group of a triose phosphate derivative issued probably from dihydroxyacetone phosphate and not from pyruvate and (ii) from a transposition step. Although this hypothetical biosynthetic pathway resembles that of L-valine biosynthesis, this amino acid or its C5 precursors could be excluded as intermediates in the formation of isoprenic units.

/pdf/isoprenoid-biosynthesis-in-bacteria-a-novel-pathway-for-the-3mkdi4hgtn.pdf

Isoprenoid biosynthesis in bacteria: a novel pathway for the early steps leading to isopentenyl diphosphate.

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(00)01433-5.pdf

Commercial potential for Haematococcus microalgae as a natural source of astaxanthin.

Ultrafast dynamics of carotenoid excited States-from solution to natural and artificial systems.

The effect of fruit maturation on changes in carotenoids, flavonoids, total soluble reducing equivalents, phenolic acids, ascorbic acid, and antioxidant activity (AOX) in different pepper types (Capsicum annuum, Capsicum frutescens, and Capsicum chinese) was determined. Generally, the concentration of these chemical constituents increased as the peppers reached maturity. Peppers contained high levels of L-ascorbic acid and carotenoids at maturity, contributing 124-338% of the RDA for vitamin C and 0.33-336 RE/100 g of provitamin A activity, respectively. Levels of phenolic acids, capxanthin, and zeaxanthin generally increased during maturation, whereas the level of lutein declined. Flavonoid concentrations varied greatly among the pepper types analyzed and were negatively correlated to AOX under the conditions of the beta-carotene-linoleic assay. Model systems were used to aid in understanding the relationship between flavonoids and AOX. Significant increases in AOX were observed in pepper juice models in response to increasing dilution factors and the presence of EDTA, indicating a pro-oxidant effect due to metal ions in the system. In vitro models demonstrated that increasing levels of flavonoids in combination with constant levels of caffeic and ascorbic acid gave a resultant AOX that was either additive of the two compounds or competitive in their ability to scavenge peroxyl radicals. The model systems were in good agreement with the chemical composition of the pepper cultivars and reflected the interactions affecting AOX. More research is needed to understand the complex interactions that occur among various antioxidants present in pepper extracts.

Changes in phytochemical and antioxidant activity of selected pepper cultivars (Capsicum species) as influenced by maturity.

The nature and biosynthesis of the carotenoids of different colour varieties of Capsicum annuum.

Stereochemistry of phytoene

Carotenoid metabolism in animals takes place as a result of enzymes which catalyse three main types of reaction. These main reaction types are (i) the substitution of carotenoid end groups (often s-end groups) by oxygen functions (-OH and -C=O), (ii) the alteration of end groups, e.g. of to c, of to K, etc. and (iii) cleavage of the polyene chain to yield apocarotenoids and even the vitamins A. Perhaps all three main reaction types are represented in the formation of the oil droplet carotenoids in the retinas of birds.

/pdf/carotenoid-metabolism-in-animals-a-biochemist-s-view-4hki612hcp.pdf

Carotenoid metabolism in animals: a biochemist's view

One of the most economically important areas within the Welsh agricultural sector is sheep farming, contributing around £230 million to the UK economy annually. Phenotypic selection over several centuries has generated a number of native sheep breeds, which are presumably adapted to the diverse and challenging landscape of Wales. Little is known about the history, genetic diversity and relationships of these breeds with other European breeds. We genotyped 353 individuals from 18 native Welsh sheep breeds using the Illumina OvineSNP50 array and characterised the genetic structure of these breeds. Our genotyping data were then combined with, and compared to, those from a set of 74 worldwide breeds, previously collected during the International Sheep Genome Consortium HapMap project. Model based clustering of the Welsh and European breeds indicated shared ancestry. This finding was supported by multidimensional scaling analysis (MDS), which revealed separation of the European, African and Asian breeds. As expected, the commercial Texel and Merino breeds appeared to have extensive co-ancestry with most European breeds. Consistently high levels of haplotype sharing were observed between native Welsh and other European breeds. The Welsh breeds did not, however, form a genetically homogeneous group, with pairwise F
 ST between breeds averaging 0.107 and ranging between 0.020 and 0.201. Four subpopulations were identified within the 18 native breeds, with high homogeneity observed amongst the majority of mountain breeds. Recent effective population sizes estimated from linkage disequilibrium ranged from 88 to 825. Welsh breeds are highly diverse with low to moderate effective population sizes and form at least four distinct genetic groups. Our data suggest common ancestry between the native Welsh and European breeds. These findings provide the basis for future genome-wide association studies and a first step towards developing genomics assisted breeding strategies in the UK.

/pdf/population-structure-and-history-of-the-welsh-sheep-breeds-48wwoc6yuc.pdf

Population structure and history of the Welsh sheep breeds determined by whole genome genotyping

Differences between the absorption spectra of ζ-carotene (7,8,7′,8′-tetrahydrolycopene) and the corresponding conjugated heptaene from diphenylamine-inhibited cultures of Rhodospirillum rubrum have been rationalized by the identification of the latter compound as the unsymmetrical isomer, 7,8,11,12-tetrahydrolycopene The structures of the other conjugated polyene hydrocarbons, phytoene, phytofluene and neurosporene, have been confirmed and a novel pathway for the dehydrogenation of phytoene to lycopene in these bacteria is described

/pdf/a-novel-sequence-for-phytoene-dehydrogenation-in-2p4luv3s5z.pdf

Brian H. Davies

Papers

The nature and biosynthesis of the carotenoids of different colour varieties of Capsicum annuum.

Stereochemistry of phytoene

Carotenoid metabolism in animals: a biochemist's view

Population structure and history of the Welsh sheep breeds determined by whole genome genotyping

A novel sequence for phytoene dehydrogenation in Rhodospirillum rubrum