Carotene synthesis from

Carotene synthesis from NaH CO or /U- C/3-PGA by chloroplasts from primary leaves of spinach. Purified chloroplasts isolated from primary leaves of 3-4 weeks old plants are... 

Two molecules of vitamin A are formed from one molecule of -carotene. Vitamin A crystallizes in pale yellow needles m.p. 64 C. It is optically inactive. It is unstable in solution when heated in air, but comparatively stable without aeration. Vitamin A is manufactured by extraction from fish-liver oils and by synthesis from / -ionone. The role of vitamin A in vision seems to be different from its systemic function. See also relincne and rhodopsin. 

In view of the synthetic importance of dicarbonvl compounds surprisingly little has been done, apart from carotene synthesis, on dialkenylation with Wittig reagents. However, from the few examples reported one may conclude, that no special problems are involved. Benzocyclobutanedione was converted by two equivalents of methoxycarbonylmethylidenetri-phenylphosphorane to the corresponding diene in 85% yield (M. P. Cava, 1960). 

Fig. 12. Light threshold of photophorogenesis in dependence of residual (3-carotene synthesis. Mycelia, 50h after inoculation, were irradiated at various fluence rates for 1 min. The threshold was determined by extrapolation. From Gal-land and Russo (1979,inpress)...

The first synthesis of a carotenoid, which was identical in structure to the dihydro-P-carotene obtainable from p-carotene (1), was successfully carried out by... 

By this route, the C10 dialdehyde, 2,7 dimethyl-2,4,6-octatriene-l,8-dial (22), is readily obtainable 26a) from 2-butene-l,4-bis(dimethylphosphonate) (19, n = 1) and methylglyoxaldimethylacetal (21). It is employed as the C10 building block in an industrially used P-carotene synthesis (see page 16). 

A new type of end-group was detected in a carotenoid from the fungus Calo-scypha fulgens Using the provional lUPAC systematic nomenclature this compound is called /i,y-carotene, (19). Its structure was proved" by synthesis from y-ionone using standard methods. y,y-Carotene was also synthesized, though as yet it has not been found in nature. 

Method of manufacture all industrial processes for preparing carotenoids are based on P-ionone. This material can be obtained by total synthesis from acetone and acetylene via dehydrolinalol. The commercially available material is usually extended on a matrix such as acacia or maltodex-trin. These extended forms of beta-carotene are dispersible in aqueous systems. Beta-carotene is also available as micronized crystals suspended in an edible oil such as peanut oil. 

Generally, the response increases with increasing concentration of the bioregulator to a maximum value. Further increases in the concentration cause no further increases in carotene content, or the bioregulator can even become somewhat inhibitory to overall carotene synthesis. Doubling of the concentration of diethylamiro-ethylphenylether from 0.26 to 0.52 M reduced the observed response... 

Tao L, Cheng Q (2004) Novel P-carotene ketolases from non-photosynthetic bacteria for canthaxanthin synthesis. Mol Gen Genomic 272 530-537... 

A great part of carotenoids in the market are from synthetic processes, as, for example, p-carotene synthesis by Wittig condensation using p-ionone as precursor, but the natural carotenoid market is growing. Both synthetic and natural carotenoids have the same molecular polyenic structure the natural compound contains several other carotenoids in low concentrations, which provides further health benefits and can be consumed in larger quantities. 

Napoli, J. L. (1990) Quantification and characteristics of retinoid synthesis from retinol and b-carotene in tissue fractions and established cell lines. Methods in Enzymol. 189,470-482. 

Precursor balancing and alteration of metabolic fluxes in the central pathways play major roles in the high-level production of metabolites. Redirection of carbon flux from pyruvate to G3P by overexpression of phosphoenolpyruvate synthase and inactivation of competing pathways resulted in improved lycopene production in E. coli [107]. In one study, P-carotene synthetic genes of Pantoea agglomerans were first integrated into the E. coli chromosome. P-Carotene synthetic pathway in recombinant E. coli was then divided into five modules P-carotene synthesis, MEP, and three central metabolic modules. Expression... 

Table 1) Activation of -carotene synthesis by a purified oxidoreductase preparation from daffodil chromoplasts Substr. phytoene (100 000 cpm = 100 o)... 

Beyer, P., Kreuz, K., Kleinig, H. (1980) 6-carotene synthesis in isolated chromoplasts from Narcissus pseudonarcissus. Plants 130, 435-438. 

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