To investigate whether, and by what mechanisms, luminal (dietary) cholesterol regulates cholesterol synthesis in human intestinal cells, HMG-CoA reductase activity, gene expression, synthesis, and degradation were investigated in CaCo-2 cells exposed to taurocholate micelles containing cholesterol. In cells incubated with cholesterol solubilized in 5 mM taurocholate and 30 microM monoolein, HMG...

Vitamin B12 is an enzymatic cofactor that essential for both eukaryotes and prokaryotes. The development of life in extreme environments depends on cofactors such as vitamin well. genomes twelve microorganisms isolated from the deep subsurface Iberian Pyrite Belt have been analyzed search activities require or are involved its synthesis import. Results revealed needed by these several enzymes r...

Using fluorescence spectroscopy, we have demonstrated that isolated envelope membranes from mature spinach chloroplasts catalyze the phototransformation of endogenous protochlorophyllide into chlorophyllide in presence of NADPH, but not in presence of NADH. Protochlorophyllide reductase was characterized further using monospecific antibodies (anti-protochlorophyllide reductase) raised against t...

A purified, active succinate-ubiquinone reductase was prepared from succinate-cytochrome c reductase without damage to ubiquinol-cytochrome c reductase by 1.1% Triton X-100 solubilization at pH 8.0, and calcium phosphate column chromatography in 50 mM Tris-succinate buffer, pH 8.0, containing 30 mM potassium phosphate. Succinate-ubiquinone reductase thus obtained contains ubiquinone and catalyz...

The interconversion of chlorophyll a and chlorophyll b, referred to as the chlorophyll cycle, plays a crucial role in the processes of greening, acclimation to light intensity, and senescence. The chlorophyll cycle consists of three reactions: the conversions of chlorophyll a to chlorophyll b by chlorophyllide a oxygenase, chlorophyll b to 7-hydroxymethyl chlorophyll a by chlorophyll b reductas...

The relationship between the NADH:lipoamide reductase and NADH:quinone reductase reactions of pig heart lipoamide dehydrogenase (EC 1.6.4.3) was investigated. At pH 7.0 the catalytic constant of the quinone reductase reaction (kcat.) is 70 s-1 and the rate constant of the active-centre reduction by NADH (kcat./Km) is 9.2 x 10(5) M-1.s-1. These constants are almost an order lower than those for ...

Activation of polyol pathway due to increased aldose reductase activity is one of the several mechanisms that have been implicated in the development of various secondary complications of diabetes. Though numerous synthetic aldose reductase inhibitors have been tested, these have not been very successful clinically. Therefore, a number of common plant/ natural products used in Indian culinary h...