Microsomal metabolism of N-nitrosodi-n-propylamine: formation of products resulting from α-and β-oxidation

We have identified propionaldehyde, n-propanol, isopropanol and N-nitroso-2-hydroxy-propylpropylamine following incubation of N-nitrosodi-n-propylamine with a microsomal fraction from rat liver. Based on the yields of the various products, we have shown that β-oxidation occurs at about 15% of the level of α-oxidation. β-as well as α-oxidation was shown to be carried out by the microsomal mixed function oxidase system. N-nitroso-2-hydroxy-propylpropylamine is further oxidized by the microsomal preparation to yield N-nitroso-2-oxopropylpropylamine.     

BiGG: a Biochemical Genetic and Genomic knowledgebase of large scale metabolic reconstructions

Background  

Genome-scale metabolic reconstructions under the Constraint Based Reconstruction and Analysis (COBRA) framework are valuable tools for analyzing the metabolic capabilities of organisms and interpreting experimental data. As the number of such reconstructions and analysis methods increases, there is a greater need for data uniformity and ease of distribution and use.     

Indirect assays for deoxyhypusine hydroxylase using dual-label ratio changes and oxidative release of radioactivity

Two procedures for rapid assay of deoxyhypusine hydroxylase activity are described. One of these assays measures changes in the 3H:14C ratio of dual-labeled protein that results from the release of tritium from a specific position in the side chain of the 3H,14C-labeled constituent amino acid deoxyhypusine upon its conversion to [3H,14C]hypusine. The other assay relies upon release of radioactivity from product protein by periodate oxidation of the radiolabeled side chain of component hypusine. The good correspondence of each of these assays with the ion exchange chromatographic method which measures hypusine and deoxyhypusine in acid hydrolysates of protein indicates that each provides a valid means of determining deoxyhypusine hydroxylase activity.     

Mapping the human CAS2 gene, the homologue of the mouse brown (b) locus, to human chromosome 9p22-pter

Melanin biosynthesis is a multistep process with the first step being the conversion of L-tyrosine to L-Dopa catalyzed by the enzyme tyrosinase. The enzymes which catalyze the other steps of melanogenesis are not known. One murine pigmentation gene, the brown (b) locus, when mutated, leads to a brown or hypopigmented coat. The b-locus protein has been shown to display catalase activity. The human b-locus, therefore, is designated as CAS2. We used the mouse b-locus cDNA to isolate the human homologue, which in turn, was used to map the CAS2 locus to a human chromosome. The potential CAS2 protein codes for 527 amino acids containing a putative signal sequence and transmembrane domain. The CAS2 protein has primary and probably secondary structures similar to human tyrosinase. The CAS2 was mapped to human Chromosome 9 by somatic cell hybridization and, more specifically, to 9p22-pter by in situ hybridization. The assignment of CAS2 on the human Chromosome 9 extends this region of known homology on mouse Chromosome 4.     

Block copolymers modify the internalization of micelle-incorporated probes into neural cells.

An important therapeutic concern is rate and extent of internalization of drugs into cells. Hydrophilic agents often internalize poorly and slowly, and highly lipophilic ones too rapidly. The incorporation of drugs into micelles allows regulation of their internalization parameters, and newly-described block copolymers can be selectively tailored to suit specific drugs. This report compares internalization of Cell Tracker CM-DiI (DiI), a highly lipophilic non-cytotoxic fluorescent probe in common use in biology, from the freely-presented (non-micelle-incorporated) and micelle-incorporated states. DiI was effectively incorporated (>60%) into 25-50 nm diameter spherical micelles made from polycaprolactone-b-polyethylene oxide block copolymer. Confocal microscopy was used to evaluate the internalization of DiI into mixed neuron-glia cultures (2-14 days in vitro, 2DIV-14DIV). Incorporation of DiI into micelles strikingly reduced the rate and extent of its internalization in both 2DIV and 14DIV cultures. Both the age of the cultures and the block copolymer employed to construct the micelles significantly influence the internalization of micelle-incorporated probe.