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F Leighton

Publications and source records attributed to F Leighton.

6 recordsLinked to original sources
PubMed1979

Detection of peroxisomal fatty acyl-coenzyme A oxidase activity.

It has been postulated that the peroxisomal fatty acid-oxidizing system [Lazarow & de Duve (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2043--2046; Lazarow (1978) J. Biol. Chem. 253, 1522--1528] resembles that of mitochondria, except for the first oxidative reaction. In this step, O2 would be directly reduced to H2O2 by an oxidase. Two specific procedures developed to detect the activity of the characteristic enzyme fatty acyl-CoA oxidase are presented, namely polarographic detection of palmitoyl-CoA-dependent cyanide-insensitive O2 consumption and palmitoyl-CoA-dependent H2O2 generation coupled to the peroxidation of methanol in an antimycin A-insensitive reaction. Fatty acyl-CoA oxidase activity is stimulated by FAD, which supports the flavoprotein nature postulated for this enzyme. Its activity increases 7-fold per g wet wt. of liver in rats treated with nafenopin, a hypolipidaemic drug. Subcellular fractionation of livers from normal and nafenopin-treated animals provides evidence for its peroxisomal localization. The stoicheiometry for palmitoyl-CoA-dependent O2 consumption, H2O2 generation and NAD+ reduction is 1 : 1 : 1. This suggests that fatty acyl-CoA oxidase is the rate-limiting enzyme of the peroxisomal fatty acid-oxidizing system.

Acyl Coenzyme A↗
PubMed1976

The similarities of ribosomal and basic chromosomal proteins from fungi.

We have compared the physical and chemical properties of yeast and fungal ribosomal proteins with those of higher eukaryotic histones. We have found that acidic urea gel electrophoresis, sodium dodecyl sulfate gel electrophoresis or chromatography on carboxymethylcellulose columns failed to distinguish ribosomal proteins from histones. The majority of the ribosomal proteins did not adsorb to an amberlite CG-50 column in the presence of 8% guanidine hydrochloride. Histones quantitatively adsorbed to an amberlite CG-50 column in the presence of 8% guanidine hydrochloride. A small number of fungal acid-soluble nuclear proteins, which coelectrophoresed with histones, were identified in a presumed nucleolar and nuclear membrane fraction. This fraction contained large amounts of RNA and small amounts of DNA. It is suggested that contamination of yeast and fungal chromosome preparations by a small number of ribosomal proteins can occur. Furthermore, several commonly employed criteria did not distinguish contaminating ribosomal proteins from authentic histones.

Binding Sites↗
PubMed1975

Structure, composition, physical properties, and turnover of proliferated peroxisomes. A study of the trophic effects of Su-13437 on rat liver.

Peroxisome proliferation has been induced with 2-methyl-2-(p-[1,2,3,4-tetrahydro-1-naphthyl]-phenoxy)-propionic acid (Su-13437). DNA, protein, cytochrome oxidase, glucose-6-phosphatase, and acid phosphatase concentrations remain almost constant. Peroxisomal enzyme activities change to approximately 165%, 50%, 30%, and 0% of the controls for catalase, urate oxidase, L-alpha-hydroxy acid oxidase, and D-amino acid oxidase, respectively. For catalase the change results from a decrease in particle-bound activity and a fivefold increase in soluble activity. The average diameter of peroxisome sections is 0.58 +/- 0.15 mum in controls and 0.73 +/- 0.25 mum after treatment. Therefore, the measured peroxisomal enzymes are highly diluted in proliferated particles. After tissue fractionation, approximately one-half of the normal peroxisomes and all proliferated peroxisomes show matric extraction with ghost formation, but no change in size. In homogenates submitted to mechanical stress, proliferated peroxisomes do not reveal increased fragility; unexpectedly, Su-13437 stabilizes lysosomes. Our results suggest that matrix extraction and increased soluble enzyme activities result from transmembrane passage of peroxisomal proteins. The changes in concentration of peroxisomal oxidases and soluble catalase after Su-13437 allow the calculation of their half-lives. These are the same as those found for total catalase, in normal and treated rats, after allyl isopropyl acetamide: about 1.3 days, a result compatible with peroxisome degradation by autophagy. A sequential increase in liver RNA concentration, [14C]leucine incorporation into DOC-soluble proteins and into immunoprecipitable catalase, and an increase in liver size and peroxisomal volume per gram liver, characterize the trophic effect of the drug used. In males, Su-13437 is more active than CPIB, another peroxisome proliferation-inducing drug; in females, only Su-13437 is active.

Acid Phosphatase↗