The sites of insertion of the transposable kanamycin-neomycin resistance-determining element, Tn5, in the E. coli K-12 chromosome were assessed in a collection of over 300 auxotrophs. Although mutations in at least 45 different cistrons were obtained, the distribution of insertion sites was not completely random: proA or proB; cysG; and cysH, cysD or cysC mutants were found in excess.

Porphyria cutanea tarda (symptomatica) (PCT) is an acquired hepatic porphyria, usually caused, in susceptible people, by liver damage from a high ethanol intake. Clinically, patients have skin fragility, hypertrichosis, photosensitivity and hyperpigmentation, and biochemically there is a high urinary excretion of uroporphyrin, hepatic siderosis, abnormal iron metabolism (Turnbull, Baker, Vernon...

The second-derivative synchronous fluorescence spectroscopic technique is applied to the simultaneous and direct assay of coproporphyrins and uroporphyrins in human urine. This technique resolves the overlapping conventional spectra, obviating the need for pre-analysis sample separation techniques, and measurements can be made in a single scan. The amplitudes of the derivative peaks are linearl...

In Saccharomyces cerevisiae, as in all eukaryotic organisms, delta-aminolevulinic acid (ALA) is a precursor of porphyrin biosynthesis, a very finely regulated pathway. ALA enters yeast cells through the gamma-aminobutyric acid (GABA) permease Uga4. The incorporation of a metabolite into the cells may be a limiting step for its intracellular metabolization. To determine the relationship between ...

We describe a simple, rapid procedure for measuring porphyrins in urine. After acidification of a urine specimen with hydrochloric acid, the second derivative of the absorption spectrum is recorded in the region of the Soret band maximum. The amplitude of the deflection is linearly related to porphyrin concentration, and the point at which the second derivative minimum occurs provides an estima...

In this quantitative assay, urinary urobilinogen is oxidized to urobilin with iodate in an acid medium, the pH is adjusted to 6 with sodium acetate, and the mixture is reacted with alcoholic HgCl2 solution, extracted with CHCl3, the measured spectrophotometrically at 513 nm. The artificial standards of previous methods have been replaced with crystalline stercobilin IX (commercially available),...

A luminol chemiluminescence method was used to evaluate the porphyrin-induced photogeneration of hydrogen peroxide (H2O2). This method enabled us to detect H202 in the presence of a high concentration of porphyrin, which was not possible using conventional colorimetry. The limit of detection was about 1 microM. We compared the ability to generate H2O2, using uroporphyrin (UP), hexacarboxylporph...

Problems encountered in the uroporphyrinogen I synthase assay were found to be due to the Triton reagent, slit-width and excitation wavelength settings of the spectrophotofluorometer, and leg-phase in the enzyme reaction. Of Triton X-100 from four suppliers, only three were found suitable. Differences in enzyme activity owing to slit-width adjustments were resolved by measuring the fluorescence...