VITAMINS

In order to investigate the conformation around the cyclohexene ring in the rhodopsin chromophore, we synthesized the bicyclic retinal analogs 7, in which C8 and C18 positions in retinal are connected by the methylene chain, and their interaction with bovine opsin was investigated. the enol triflates 17 which were readily derived from the bicyclic ketones 11 prepared from 2,2-dimethylcyclohexanone 9 via Dieckmann condensation of the diesters 10, were treated with methyl E-3-trimethylstannyl-2-butenoate in the presence of palladium diacetate to afford the β-ionylideneacetate ester analogs 18. These compounds were converted to the corresponding retinal analogs 7 via the Witting salts 22 and pentaenyl esters 23 or nitrile 26. The binding experiments of the retinal analogs 7 with bovine opsin gave the new artificial pigments 8 and from the comparison of opsin shift values, it was substantiated that the torsional angle around the 6-7 single bond in the rhodopsin chromophore is very close to that of rhodopsin analog 8b having a seven membered ring.

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Vitamin B_1 is essential for growth of Euglena gracilis, a unicellular photosynthetic organism, which has both the characteristics of plant and animal. Euglena take up actively vitamin B_1 and pyrimidine moiety of thiamin, since this organism is possible to synthesize the thiazole moiety. Convertion of vitamin B_1 or the analogues to coenzyme is achieved in the participation of thiaminase II and thiamin pyrophosphokinase. In the metabolism of 2-oxo acids in E. gracilis pyruvate and 2-oxoglutarate dehydrogenase complexes are not involved, but pyruvate : NADP^+ oxidoreductase and 2-oxoglutarate decarboxylase participates in an alternative tricarboxylic acid metabolism which is composed of succinate semialdehyde dehydrogenase to catalyze further the convertion of succinate semialdehyde to succinate. Furthermore pyruvate : NADP^+ oxidoreductase is included in the wax ester fermentation which is an energy-generating system in anoxia. NAD^+ is known well to function as a cofactor in oxidation and reduction in all organisms, and further participate in metabolic regulation and signal transduction through ADP-ribosylation enzyme which catalyzes the transfer of ADP-ribose cyclase to release nicotinamide from NAD^+, according to Ca^<2+> release from intracellular Ca^<2+> stores. In Euglena a specific ADP-ribosylation to the arginine residue was shown to play an important role in S phase and G_2-M transition of cell division. Consequently polymerization of micro-tubules was completely inhibited by ADP-ribosylation in Euglena. cADP-ribose and the synthesizing enzyme, ADP-ribose cyclase, increased remarkably in the G_2 phase of cell division cycle but not inositol trisphosphate, suggesting that cADP-ribose functions as a regulator of cell division through mediating endogenious Ca^<2+> release.

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Relationship between serum levels of lipid peroxides and carotenoids among the subjects randomly selected from the residents living in T-city, Gifu (GT), T-town, Wakayama (TW), H-city Hiroshima (HH), S-town, Fukuoka (SF), and Y-town, Hokkaido (HY) was investigated cross-sectionally. It was demonstrated that serum levels of β-carotene or cryptoxanthin were higher for GT and HY residents or for WT residents, while serum levels of lipid peroxides estimated by the thiobarbituric acid-reactive substances (TBARS) were lower for GT and HY residents, respectively. Moreover, there were some regional differences that serum levels of carotenoids such as β-carotene were inversely associated with serum TBARS levels for the residents, but not for HH residents with encumbrances of Japanese Americans. Serum TBARS levels were positively and significantly related with serum levels of n-3 unsaturated fatty acids such as icosapentaenoic acid and docosahexaenoic acid, which were high intake in Japanese, but not significantly with serum levels of n-6 unsaturated fatty acids such as arachidonic acid.

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