Biomaterial Database

Membrane charge as effector of cytochrome P-450LM2 catalyzed reactions in reconstituted liposomes. 1981

M Ingelman-Sundberg, and T Haaparanta, and J Rydström

The phospholipid specificity of rabbit liver microsomal cytochrome P-450LM2 catalyzed hydroxylation reactions was examined in reconstituted phospholipid vesicles. An apparent linear relationship between the negative charge of the vesicles and the rate of P-450LM2-catalyzed O-dealkylation of p-nitroanisole or 7-ethoxycoumarin was obtained. The membrane charge-mediated increase in hydroxylation activities was found not to be due to (i) an altered lipid/water partition coefficient of the substrate, (ii) a change in the apparent Michaelis constant of P-450LM2 for the substrate, (iii) a different activation energy of the O-demethylation of p-nitroanisole, (iv) different spin states of P-450LM2 or (v) an altered secondary structure of this enzyme as monitored by circular dichroism. However, when the formation of the ferrous carbonyl complex of P-450LM2 was followed under aerobic or anaerobic conditions after the addition of NADPH to the vesicles, an increased negative charge of the membrane was accompanied by an increased reducibility of P-450LM2. A similar linear relationship between the reducibility of cytochrome b5 and the negative charge of the liposomes was also evident in membranes containing NADPH-cytochrome P-450 reductase and cytochrome b5. It is proposed that the interaction of the reductase with P-450LM2 is inefficient in neutral vesicles and thus rate determining for the overall hydroxylation activities.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008081	Liposomes	Artificial, single or multilaminar vesicles (made from lecithins or other lipids) that are used for the delivery of a variety of biological molecules or molecular complexes to cells, for example, drug delivery and gene transfer. They are also used to study membranes and membrane proteins.	Niosomes,Transferosomes,Ultradeformable Liposomes,Liposomes, Ultra-deformable,Liposome,Liposome, Ultra-deformable,Liposome, Ultradeformable,Liposomes, Ultra deformable,Liposomes, Ultradeformable,Niosome,Transferosome,Ultra-deformable Liposome,Ultra-deformable Liposomes,Ultradeformable Liposome
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D010105	Oxygenases	Oxidases that specifically introduce DIOXYGEN-derived oxygen atoms into a variety of organic molecules.	Oxygenase
D010743	Phospholipids	Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.	Phosphatides,Phospholipid
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D003374	Coumarins	Synthetic or naturally occurring substances related to coumarin, the delta-lactone of coumarinic acid.	1,2-Benzopyrone Derivatives,1,2-Benzopyrones,Coumarin Derivative,Coumarine,1,2-Benzo-Pyrones,Benzopyran-2-ones,Coumarin Derivatives,Coumarines,1,2 Benzo Pyrones,1,2 Benzopyrone Derivatives,1,2 Benzopyrones,Benzopyran 2 ones,Derivative, Coumarin,Derivatives, 1,2-Benzopyrone,Derivatives, Coumarin
D003577	Cytochrome P-450 Enzyme System	A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.	Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships