Biomedical subjects

Vasily D Antonenkov

Publications and source records attributed to Vasily D Antonenkov.

5 recordsLinked to original sources

PubMed2006

Peroxisomal membrane permeability and solute transfer.

The review is dedicated to recent progress in the study of peroxisomal membrane permeability to solutes which has been a matter of debate for more than 40 years. Apparently, the mammalian peroxisomal membrane is freely permeable to small solute molecules owing to the presence of pore-forming channels. However, the membrane forms a permeability barrier for 'bulky' solutes including cofactors (NAD/H, NADP/H, CoA, and acetyl/acyl-CoA esters) and ATP. Therefore, peroxisomes need specific protein transporters to transfer these compounds across the membrane. Recent electrophysiological studies have revealed channel-forming activities in the mammalian peroxisomal membrane. The possible involvement of the channels in the transfer of small metabolites and in the formation of peroxisomal shuttle systems is described.

Adenosine Triphosphate↗

PubMed2006

Peroxisomal beta-oxidation--a metabolic pathway with multiple functions.

Fatty acid degradation in most organisms occurs primarily via the beta-oxidation cycle. In mammals, beta-oxidation occurs in both mitochondria and peroxisomes, whereas plants and most fungi harbor the beta-oxidation cycle only in the peroxisomes. Although several of the enzymes participating in this pathway in both organelles are similar, some distinct physiological roles have been uncovered. Recent advances in the structural elucidation of numerous mammalian and yeast enzymes involved in beta-oxidation have shed light on the basis of the substrate specificity for several of them. Of particular interest is the structural organization and function of the type 1 and 2 multifunctional enzyme (MFE-1 and MFE-2), two enzymes evolutionarily distant yet catalyzing the same overall enzymatic reactions but via opposite stereochemistry. New data on the physiological roles of the various enzymes participating in beta-oxidation have been gathered through the analysis of knockout mutants in plants, yeast and animals, as well as by the use of polyhydroxyalkanoate synthesis from beta-oxidation intermediates as a tool to study carbon flux through the pathway. In plants, both forward and reverse genetics performed on the model plant Arabidopsis thaliana have revealed novel roles for beta-oxidation in the germination process that is independent of the generation of carbohydrates for growth, as well as in embryo and flower development, and the generation of the phytohormone indole-3-acetic acid and the signal molecule jasmonic acid.

Acetyl-CoA C-Acyltransferase↗

PubMed2006

Localization of a portion of the liver isoform of fatty-acid-binding protein (L-FABP) to peroxisomes.

The liver isoform of fatty-acid-binding protein (L-FABP) facilitates the cellular uptake, transport and metabolism of fatty acids and is also involved in the regulation of gene expressions and cell differentiation. Consistent with these functions, L-FABP is predominantly present in the cytoplasm and to a lesser extent in the nucleus; however, a significant portion of this protein has also been detected in fractions containing different organelles. More recent observations, notably on L-FABP-deficient mice, indicated a possible direct involvement of L-FABP in the peroxisomal oxidation of long-chain fatty acids. In order to clarify the links between L-FABP and peroxisomal lipid metabolism, we reinvestigated the subcellular distribution of the protein. Analytical subcellular fractionation by a method preserving the intactness of isolated peroxisomes, two-dimensional gel electrophoresis of peroxisomal matrix proteins combined with MS analysis, and immunoelectron microscopy of liver sections demonstrate the presence of L-FABP in the matrix of peroxisomes as a soluble protein. Peroxisomal L-FABP was highly inducible by clofibrate. The induction of L-FABP was accompanied by a marked increase in the binding capacity of peroxisomal matrix proteins for oleic acid and cis-parinaric acid. The peroxisomal beta-oxidation of palmitoyl-CoA and acyl-CoA thioesterase activity were stimulated by L-FABP, indicating that the protein modulates the function of peroxisomal lipid-metabolizing enzymes. The possible role of intraperoxisomal L-FABP in lipid metabolism is discussed.

Animals↗

PubMed2004

The rat liver peroxisomal membrane forms a permeability barrier for cofactors but not for small metabolites in vitro.

The functional role of the peroxisomal membrane as a permeability barrier to metabolites has been a matter of controversy for more than four decades. The initial conception, claiming free permeability of the membrane to small solute molecules, has recently been challenged by several observations suggesting that the peroxisomal membrane forms a closed compartment. We have characterized in vitro the permeability of rat liver peroxisomal membrane. Our results indicate that the membrane allows free access into peroxisomes for small hydrophilic molecules, such as substrates for peroxisomal enzymes (glycolate, urate), but not to more bulky cofactors (NAD/H, NADP/H, CoA). Although access for cofactors is not prevented completely by the membrane, the membrane barrier severely restricts their rate of entry into peroxisomes. The data lead to conclusion that, in vivo, peroxisomes may possess their own pool of cofactors, while they share a common pool of small metabolites with the cytoplasm. The results also indicate that molecular size plays an important role in in vivo distinction between cofactors and metabolic intermediates.

Animals↗

PubMed2004

The behavior of peroxisomes in vitro: mammalian peroxisomes are osmotically sensitive particles.

It has been known for a long time that mammalian peroxisomes are extremely fragile in vitro. Changes in the morphological appearance and leakage of proteins from purified particles demonstrate that peroxisomes are damaged during isolation. However, some properties of purified peroxisomes, e.g., the latency of catalase, imply that their membranes are not disrupted. In the current study, we tried to ascertain the mechanism of this unusual behavior of peroxisomes in vitro. Biochemical and morphological examination of isolated peroxisomes subjected to sonication or to freezing and thawing showed that the membrane of the particles seals after disruption, restoring permeability properties. Transient damage of the membrane leads to the formation of peroxisomal "ghosts" containing nucleoid but nearly devoid of matrix proteins. The rate of leakage of matrix proteins from broken particles depended inversely on their molecular size. The effect of polyethylene glycols on peroxisomal integrity indicated that these particles are osmotically sensitive. Peroxisomes suffered an osmotic lysis during isolation that was resistant to commonly used low-molecular-mass osmoprotectors, e.g., sucrose. Damage to peroxisomes was partially prevented by applying more "bulky" osmoprotectors, e.g., polyethylene glycol 1500. A method was developed for the isolation of highly purified and nearly intact peroxisomes from rat liver by using polyethylene glycol 1500 as an osmoprotector.

Alcohol Dehydrogenase↗