Conversion of progesterone to corticosteroids by the midterm fetal adrenal and kidney

Midterm fetal adrenal and kidney tissue homogenates were incubated with 3H-progesterone (1 microM) and its conversion to te 3H-corticosteroids metabolites studied. Cortisol (36.3%) and corticosterone (4.7%) were isolated from the adrenal, and 11-deoxycortisol (32.5%) and deoxycorticosterone (21.1%) from the kidney. The results of these incubations confirmed the presence of 17- and 21-hydroxylase activities in both fetal tissues, and that of 11 beta-hydroxylase activity only in fetal adrenal tissue. We conclude that during pregnancy when progesterone levels are high, biosynthesis by the fetal kidney of 11-deoxycortisol, the most abundant corticosteroid formed by this tissue in this investigation, might provide to the fetal adrenal an important precursor for cortisol biosynthesis within the fetal compartment.     

Metabolism of 2-amino-3-phosphono[3-14C]propionic acid in cell-free preparations of rat liver.

Incubation of 2-amino-3-phosphono[3-14C]propionic acid with cell-free preparations of rat liver yielded labelled 3-phosphonopyruvic acid, 2-phosphonoacetaldehyde, 2-aminoethylphosphonic acid and acetaldehyde. No radioactivity was found in phosphoenolpyruvate, pyruvic acid, alanine, and phosphonoacetic acid. When added to the cell-free preparations, 3-phosphonopyruvic acid trapped the radioactivity, resulting in decrease of incorporation of the radioactivity into 2-phosphonoacetaldehyde, 2-aminoethylphosphonic acid and acetaldehyde. Incorporation of the radioactivity into 2-aminoethylphosphonic acid and acetaldehyde was also decreased by 2-phosphonoacetaldehyde. Thus it appears that the main metabolic pathway of 2-amino-3-phosphonopropionic acid is deamination to produce 3-phosphonopyruvic acid which is, in turn, converted to 2-phosphonoacetaldehyde by decarboxylation, followed by both dephosphonylation and amination of the aldehyde to give acetaldehyde and 2-aminoethylphosphonic acid, respectively.     

Conversion of xanthoxin to abscisic Acid by cell-free preparations from bean leaves

Cell-free extracts from the leaves of Phaseolus vulgaris L. convert xanthoxin to abscisic acid. The enzyme activity in dialyzed or acetone-precipitated extracts shows a strong dependence on either NAD or NADP. The enzyme activity appears to be cytosolic with no significant activity observed in chloroplasts. The activity was observed in extracts from roots of Phaseolus vulgaris, and also in extracts prepared from the leaves of Pisum sativum L., Zea mays L., Cucurbita maxima Duchesne, and Vigna radiata L. Neither water stress nor cycloheximide appear to significantly affect the level of enzyme activity in leaves. No intermediates between xanthoxin and abscisic acid were detected.     

Interrenal function during amphibian metamorphosis: in vitro biosynthesis of radioactive corticosteroids from (4(14)C)-progesterone by interrenal in Xenopus laevis tadpoles

Whole kidneys of Xenopus laevis tadpoles (containing interrenal cells) or the outer postero-dorsal part of adult kidney (containing a few or no interrenal cells) were incubated with (4(14)C)-progesterone. Methylene chloride extractable radioactivity of tissue homogenates in their incubation medium were purified by sequential paper chromatography and identification of some isolated fractions was attempted. A significant conversion of progesterone was only observed when interrenals were present in incubation; however, possible steroidogenic activity of the other tissue types present in the kidney cannot be ignored. At all the developmental stages of tadpoles (from stage 45 to stage 66) and in juveniles, the same steroids were isolated. Hence the metabolic pathways for corticosteroidogenesis in Xenopus laevis remained unchanged during metamorphosis and several weeks after the end of this process. Aldosterone was identified. Corticosterone and 11-dehydrocorticosterone were also synthesized but not completely purified. Their yields were always larger than those of aldosterone. Cortisol was never detected.     

Conversion of leukotrienes A4 to C4 in cell-free systems

A procedure for assaying leukotriene C4 synthase activity in cell-free extracts has been presented. Leukotriene A4 methyl ester was as active a substrate as leukotriene A4 (Na salt) for the synthesis. The methyl ester is the substrate of choice, because (1) it is more stable than the sodium salt, (2) it is not a substrate of epoxide hydrolase for leukotriene B4 synthesis, and (3) it gives a lower blank than an equimolar concentration of leukotriene A4. The enzyme activity in rat liver, guinea pig and human lungs, and human nasal polyp was chiefly membrane-bound, although the cytosol contained some activity.     

Conversion of [14C]gibberellin A12-aldehyde to C19- and C20-gibberellins in a cell-free system from immature seed of Phaseolus coccineus L.

A cell-free system prepared from developing seed of runner bean (Phaseolus coccineus L.) converted [¹⁴C]gibberellin A₁₂-aldehyde to several products. Thirteen of these were identified by capillary gas chromatography-mass spectrometry as gibberellin A₁ (GA₁), GA₄, GA₅, GA₆, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₄, GA₃₇, GA₃₈, GA₄₄ and GA₅₃-aldehyde, all giving mass spectra with ¹⁴C-isotope peaks. GA₈ and GA₂₈ were also identified but contained no ¹⁴C. All the [¹⁴C]GA₁₂-aldehyde metabolites, except GA₁₅, GA₂₄ and GA₅₃-aldehyde, are known endogenous GAs of P. coccineus.Abbreviations GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC highperformance liquid chromatography - MVA mevalonic acid - S-2 2000-g supernatant