Biocatalytic Synthesis of Dihydroxynaphthoic Acids by Cytochrome P450 CYP199A2

CYP199A2, a bacterial P450 monooxygenase from Rhodopseudomonas palustris, was found to exhibit oxidation activity towards three hydroxynaphthoic acids. Whole cells of the recombinant Escherichia coli strain expressing CYP199A2 efficiently catalyzed the regioselective oxidation of 1-, 3-, and 6-hydroxy-2-naphthoic acids to produce 1,7-, 3,7-, and 6,7-dihydroxynaphthoic acid respectively. These results suggest that CYP199A2 might be a useful oxidation biocatalyst for the synthesis of dihydroxynaphthoic acids.     

Crystalline 2-Ketogluconate Reductase from Acetobacter ascendens,the Second Instance of Crystalline Enzyme in Genus Acetobacter

Crystalline 2-ketogluconate reductase in genus Acetobacter was prepared from cell free extract of Acetobacter ascendens. Crystalline enzyme was purified 13,000-fold with a yield of 15%. Affinity chromatography on blue-dextran Sepharose 4B column successfully purified the enzyme. The enzyme was composed of three identical subunits with a molecular weight of 40,000. Substrate specificity of 2-ketogluconate reductase from two genera of acetic acid bacteria was compared using highly purified enzyme preparations, and it was confirmed that gluconate oxidation activity of the enzyme was intrinsically weak or absent in genus Acetobacter and intense in Gluconobacter. This fact must be a useful criterion for classification of acetic acid bacteria.     

Ferredoxin-dependent Sulfite Reductase from Spinach Leaves

The intermediate of the aromatization of 4-oxocyclohexanecar-boxylic acid (OHA) to 4-hydroxybenzoic acid (HA) by Coryne-bacterium cyclohexanicum was identified as (+)-4-oxocyclohex-2-enecarboxylic acid (O2A) using a combined system of gas-liquid chromatography (GLC) and a mass spectrometer and polarimeter.     

Volatile Gas Components Contribute to Cigarette Smoke-induced DNA Single Strand Breaks in Cultured Human Cells

Thermostable purine nucleoside phosphorylases, PUN PI and PUNPII, have been purified from Bacillus stearothermophilus JTS 859. The characterization of PUNPI was reported previously. [Hori et al.₉ Agric. Biol. Chem. 53, 2205 (1989)] PUNPII had a molecular weight of 113,000, consisting of 4 identical subunits (M_w 28,000). The isoelectric point was 5.3. The Michaelis constants for inosine, guanosine, and adenosine were 0.22, 0.34, and 0.075 mm, respectively. The optimal temperature of the reaction was 70°C. The enzyme was stable at 70°C. Although other reported purine nucleoside phosphorylases were SH-enzymes, PUNPII was not a SH-enzyme because the enzyme reaction was not inhibited by PCMB and iodoacetic acid, the optimal pH of the enzyme reaction was from 7.0 to 11.0, and the enzyme did not contain cysteine.

PUNPII and PUNPI were different in several points. Not PUNPI but PUNPII could catalyze the phosphorolysis of adenosine. Specific activity of PUNPI and II for inosine were 405 and 50.6 μmol/min/mg protein at 60°C, respectively. PUNPI was stable at 80°C. PUNPII was stable at 70°C, but was denatured at 80°C.     

Inhibition of malaria parasite growth by quinomycin A and its derivatives through DNA-intercalating activity

Quinomycin A and its derivatives were identified as potent antimalarial (Plasmodium falciparum) agents in a screen of the RIKEN NPDepo chemical library. IC₅₀ values of quinomycin A and UK-63,598 were approximately 100 times lower than that of the antimalarial drug chloroquine. This activity was mitigated by the addition of plasmid DNA, suggesting that these compounds act against parasites by intercalating into their DNA.     

Effects of Korean Red Ginseng extract on hepatic lipid accumulation in HepG2 cells

In this study, we investigated the effects of Korean red ginseng water extract (KRGE) on hepatic lipid accumulation in HepG2 cells. KRGE decreased hepatic triglyceride and cholesterol levels. Further, KRGE suppressed expression of fatty acid synthase (FAS) and 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase. These results suggest that KRGE may reduce hepatic lipid accumulation by inhibition of FAS and HMG-CoA reductase expression in HepG2 cells.     

Importance of Dietary Cholesterol for the Maturation of Mouse Brain Myelin

The effect of nil (control), 1% (CH-l) and 5% (CH-5) dietary cholesterol on the myelination of mouse brain, and its deposition in the heart and liver were investigated during infancy. Swiss Webstar female mice were given formulated diets from early gestation, and their pups were weaned on the same diet as that of the individual mothers up to 60 days after birth. The test diets increased the liver weight and cholesterol content compared to the control even in suckling pups (20 days), but did not significantly influence the heart weight until 60 days. The cholesterol content of the heart was not increased by the CH-l diet throughout the feeding period, but it did increase the mole ratio of major myelin lipids and hastened its maturation. Myelin cholesterol was 10% higher in 20-day-old suckling pups in the CH-5 group compared to the control. Data indicate that dietary cholesterol altered the brain myelination rate of weaning mice, and that the mother’s dietary cholesterol influenced myelination of the suckling pups.     

In Vitro and in Vivo Melanogenesis Inhibition by Biochanin A from Trifolium pratense

Our previous study showed that a methanol extract from Trifolium pratense exerted potent inhibitory activity on melanogenesis in mouse B16 melanoma cells. In the present study, the active compound in this Chinese herb extract was isolated and identified as biochanin A by mass spectrum, ¹H-NMR, and ¹³C-NMR analysis. The inhibitory effects of biochanin A on melanogenesis were investigated in vitro in cultured melanoma cells and in vivo in zebrafish and mice. Biochanin A dose-dependently inhibited both melanogenesis and cellular tyrosinase activity in B16 cells and in zebrafish embryos. Application of a cream containing 2% biochanin A twice daily to the skin of mice also increased the skin-whitening index value after 1 week of treatment, and the increase continued for another 2 weeks. Biochanin A was confirmed as a good candidate for use as a skin-whitening agent in the treatment of skin hyperpigmentation disorders.