Degradation of FATTY ACID EXPORT PROTEIN1 by RHOMBOID-LIKE PROTEASE11 contributes to cold tolerance in Arabidopsis.

Plants need to acclimate to different stresses to optimize growth under unfavorable conditions. In Arabidopsis (Arabidopsis thaliana), the abundance of the chloroplast envelope protein FATTY ACID EXPORT PROTEIN1 (FAX1) decreases after the onset of low temperatures. However, how FAX1 degradation occurs and whether altered FAX1 abundance contributes to cold tolerance in plants remains unclear.

Fatty acid export (FAX) proteins contribute to oil production in the green microalga .

In algae and land plants, transport of fatty acids (FAs) from their site of synthesis in the plastid stroma to the endoplasmic reticulum (ER) for assembly into acyl lipids is crucial for cellular lipid homeostasis, including the biosynthesis of triacylglycerol (TAG) for energy storage. In the unicellular green alga , understanding and engineering of these processes is of particular interest for microalga-based biofuel and biomaterial production. Whereas in the model plant , FAX (fatty acid export) proteins have been associated with a function in plastid FA-export and hence TAG synthesis in the ER, the knowledge on the function and subcellular localization of this protein family in Chlamydomonas is still scarce.

Underestimated reactions and regulation patterns of adrenal cytochromes P450.

Although cytochrome P450 (CYP) systems including the adrenal ones are being investigated since many years, there are still reactions and regulation patterns that have been underestimated ever since. This review discusses neglected ones to bring them into the focus of investigators working in the field. Novel substrates and reactions described for adrenal CYPs recently point to the fact that different from what has been believed for many years, adrenal CYPs are less selective than previously thought.

Plant membrane-protein mediated intracellular traffic of fatty acids and acyl lipids.

In plants, de novo synthesis of fatty acids (FAs) occurs in plastids, whereas assembly and modification of acyl lipids is accomplished in the endoplasmic reticulum (ER) and plastids as well as in mitochondria. Subsequently, lipophilic compounds are distributed within the cell and delivered to their destination site. Thus, constant acyl-exchanges between subcellular compartments exist.

The impact of the clinical CYP11B2 mutation V386A strongly depends on the enzyme's genetic background.

Human cytochrome P450 11B2 (CYP11B2) is an essential enzyme in the steroid hormone biosynthesis, which catalyzes the last three reaction steps of the aldosterone synthesis. These reactions comprise a hydroxylation at position C11 of the steroid intermediate deoxycorticosterone yielding corticosterone, followed by a hydroxylation at position C18 yielding 18-hydroxy-corticosterone and a subsequent oxidation of the hydroxyl group at C18, which results in the formation of aldosterone. Alterations in the amino acid sequence of CYP11B2 often cause severe disease patterns.

Role of steroid sulfatase in steroid homeostasis and characterization of the sulfated steroid pathway: Evidence from steroid sulfatase deficiency.

The impact of steroid sulfatase (STS) activity in the circulating levels of both sulfated and unconjugated steroids is only partially known. In addition, the sulfated steroid pathway, a parallel pathway to the one for unconjugated steroids, which uses the same enzymes, has never been characterized in detail before. Patients with steroid sulfatase deficiency (STSD) are unable to enzymatically convert sulfated steroids into their unconjugated forms, and are a good model to elucidate how STS affects steroid biosynthesis and to study the metabolism of sulfated steroids.

The role of sulfated steroid hormones in reproductive processes.

Sulfated steroid hormones, such as dehydroepiandrosterone sulfate or estrone-3-sulfate, have long been regarded as inactive metabolites as they cannot activate classical steroid receptors. Some of them are present in the blood circulation at quite high concentrations, but generally sulfated steroids exhibit low membrane permeation due to their hydrophilic properties. However, sulfated steroid hormones can actively be imported into specific target cells via uptake carriers, such as the sodium-dependent organic anion transporter SOAT, and, after hydrolysis by the steroid sulfatase (so-called sulfatase pathway), contribute to the overall regulation of steroid responsive organs.

A Novel NADPH-dependent flavoprotein reductase from Bacillus megaterium acts as an efficient cytochrome P450 reductase.

Cytochromes P450 (P450s) require electron transfer partners to catalyze substrate conversions. With regard to biotechnological approaches, the elucidation of novel electron transfer proteins is of special interest, as they can influence the enzymatic activity and specificity of the P450s. In the current work we present the identification and characterization of a novel soluble NADPH-dependent diflavin reductase from Bacillus megaterium with activity towards a bacterial (CYP106A1) and a microsomal (CYP21A2) P450 and, therefore, we referred to it as B.

Metabolism of Oral Turinabol by Human Steroid Hormone-Synthesizing Cytochrome P450 Enzymes.

The human mitochondrial cytochrome P450 enzymes CYP11A1, CYP11B1, and CYP11B2 are involved in the biosynthesis of steroid hormones. CYP11A1 catalyzes the side-chain cleavage of cholesterol, and CYP11B1 and CYP11B2 catalyze the final steps in the biosynthesis of gluco- and mineralocorticoids, respectively. This study reveals their additional capability to metabolize the xenobiotic steroid oral turinabol (OT; 4-chlor-17β-hydroxy-17α-methylandrosta-1,4-dien-3-on), which is a common doping agent.

Dehydroepiandrosterone sulfate (DHEAS) stimulates the first step in the biosynthesis of steroid hormones.

Dehydroepiandrosterone sulfate (DHEAS) is the most abundant circulating steroid in human, with the highest concentrations between age 20 and 30, but displaying a significant decrease with age. Many beneficial functions are ascribed to DHEAS. Nevertheless, long-term studies are very scarce concerning the intake of DHEAS over several years, and molecular investigations on DHEAS action are missing so far.