Chan-Shick Kim

Isolation and characterization of cDNAs encoding β-carotene hydroxylase in Citrus☆

Abstract Citrus ( Citrus unshiu Marc.) contains high contents (0.45–5.26 mg%) of β-cryptoxanthin. cDNA clones ( CHX1 and CHX2 ) encoding β-carotene hydroxylase (Chx) were isolated from Citrus fruit and leaf cDNA libraries. Sequence analyses indicated that the clones show polymorphism and that cDNA contains an open reading frame encoding 311 amino acids (34 kDa). Phylogenetic dendrogram suggested the evolutionary link among the fruit-producing plants. RNA blot analysis showed that its expression is ubiquitous in three tissues examined — fruits, leaves, and flowers — and that it is detected as a single band. Also, during the development of fruits and leaves, the expression of CHX1 and CHX2 transcripts was consistent in all stages, which indicated that CHX1 and CHX2 genes are not regulated during fruit ripening at the transcriptional level and revealed that their expression varies with plant species, even having the same type of fruit. Our results suggest that the expression of Chx at the transcriptional level does not contribute to the changes of carotenoids biosynthesis in ripening fruit of Citrus .

Inhibitory effect of Jeju endemic seaweeds on the production of pro-inflammatory mediators in mouse macrophage cell line RAW 264.7.

Seaweed has been used in traditional cosmetics and as a herbal medicine in treatments for cough, boils, goiters, stomach ailments, and urinary diseases, and for reducing the incidence of tumors, ulcers, and headaches. Despite the fact that seaweeds are frequently used in the practice of human health, little is known about the role of seaweed in the context of inflammation. This study aimed to investigate the influence of Jeju endemic seaweed on a mouse macrophage cell line (RAW 264.7) under the stimulation of lipopolysaccharide (LPS). Ethyl acetate extracts obtained from 14 different kinds of Jeju seaweeds were screened for inhibitory effects on pro-inflammatory mediators. Our results revealed that extracts from five seaweeds, Laurencia okamurae, Grateloupia elliptica, Sargassum thunbergii, Gloiopeltis furcata, and Hizikia fusiformis, were potent inhibitors of the production of pro-inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Based on these results, the anti-inflammatory effects and low cell toxicity of these seaweed extracts suggest potential therapeutic applications in the regulation of the inflammatory response.

Isolation and expression patterns of a cDNA encoding phytoene synthase in Citrus

Summary A cDNA clone (Psy1) encoding phytoene synthase was isolated from the fruit cDNA library ofCitrus (Citrus unshiuMarc.). Sequence analyses and phylogenetic dendrogram revealed that the cDNA contains an open reading frame encoding 437 amino acids (47 kDa), which showed significant similarity to those of phytoene synthases of fruit-producing plants. RNA blot analysis showed that the mRNA is expressed in the edible parts and peels of fruits, leaves, and flowers, as a single transcript. Also, during the ripening of fruits, thePsy1 transcripts were detected in all stages and its expression markedly increased to the maximum level in the latest stage. A similar pattern was also detected in peels. Also, the level ofPsy1 transcripts is changed in the process of leaf development. Our results suggested that Psy1 is an important regulatory enzyme in carotenoid accumulation during fruit ripening. This is the first report to characterize the relationship between the expression ofPsy and fruit development in a woody plant.

A New In Vitro Assay of Cholesterol Adsorption by Food and Microbial Polysaccharides

The adsorption of total cholesterol by polysaccharides was measured in vitro by enzymatic reactions, including the polysaccharide precipitation procedure. Total cholesterol adsorption capacities, in a mixture of polysaccharide and total cholesterol, were compared for apple pectin, gelrite gellan gum, xanthan gum, high-methoxyl pectin, citrus pectin, high-viscous alginate, low-viscous alginate, dextran, and zooglan. Acidic polysaccharides such as pectins, alginate, and xanthan gum at concentrations of 0.1% (wt/vol) were able to adsorb over 90% of the total cholesterol when dissolved in distilled water, sodium acetate buffer (pH 4.6), or sodium phosphate buffer (pH 7.0). However, total cholesterol adsorptions by gellan and zooglan were dependent upon the salt concentration and pH value, which decreased cholesterol adsorption in the following order by degree: distilled water, acidic pH, and alkaline pH. In particular, total cholesterol adsorption of zooglan was greatly decreased by the addition of sodium chloride. With 0.1% (wt/vol) polysaccharide dissolved in distilled water, the adsorption capacities of alginate, pectins, gellan gum, xanthan gum, and zooglan were 2.9, 2.88, 2.5, 2.9, and 2.4 mg/dL, respectively. However, 0.2% of zooglan was able to completely adsorb the cholesterol (3 mg/dL), whereas dextran did not adsorb cholesterol at all, producing no precipitate with hexadecyltrimethylammonium bromide.