Biomaterial Database

Alteration of enzymes in ageing human fibroblasts in culture. II. Conditions for the reversibility and the mechanism of the alteration of glucose 6-phosphate dehydrogenase. 1984

A Houben, and M Raes, and A Houbion, and J Remacle

The appearance of a heat-labile glucose 6-phosphate dehydrogenase fraction can be induced by incubation of human fibroblasts at 4 degrees C and pH 7.4. Using this system we first studied the effects of pH and NADP+ on the reversibility of the alteration. In young cells, the induced alteration of glucose 6-phosphate dehydrogenase disappeared if the pH of the medium was lowered to 6.5 or if NADP+ was added. In old cells, the disappearance of the natural heat-labile glucose 6-phosphate dehydrogenase was possible only if both pH 6.5 and NADP+ were present. Secondly, we studied the effects of the alteration and its reversibility on the equilibrium between the enzyme subunits; we showed that alteration and inactivation are linked to a dissociation of the enzyme subunits into inactive monomers. We also proposed a model where the heat-labile enzyme is a transient form between the active dimer and inactive monomer. Our results are in perfect agreement with the theories of post-translational modifications now proposed to explain the presence of the altered enzymes in old cells.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D009249	NADP	Nicotinamide adenine dinucleotide phosphate. A coenzyme composed of ribosylnicotinamide 5'-phosphate (NMN) coupled by pyrophosphate linkage to the 5'-phosphate adenosine 2',5'-bisphosphate. It serves as an electron carrier in a number of reactions, being alternately oxidized (NADP+) and reduced (NADPH). (Dorland, 27th ed)	Coenzyme II,Nicotinamide-Adenine Dinucleotide Phosphate,Triphosphopyridine Nucleotide,NADPH,Dinucleotide Phosphate, Nicotinamide-Adenine,Nicotinamide Adenine Dinucleotide Phosphate,Nucleotide, Triphosphopyridine,Phosphate, Nicotinamide-Adenine Dinucleotide
D002470	Cell Survival	The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.	Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D005347	Fibroblasts	Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules.	Fibroblast
D005954	Glucosephosphate Dehydrogenase		Glucose-6-Phosphate Dehydrogenase,Dehydrogenase, Glucose-6-Phosphate,Dehydrogenase, Glucosephosphate,Glucose 6 Phosphate Dehydrogenase
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D046508	Culture Techniques	Methods of maintaining or growing biological materials in controlled laboratory conditions. These include the cultures of CELLS; TISSUES; organs; or embryo in vitro. Both animal and plant tissues may be cultured by a variety of methods. Cultures may derive from normal or abnormal tissues, and consist of a single cell type or mixed cell types.	Culture Technique,Technique, Culture,Techniques, Culture