Biomaterial Database

Evidence of an essential carboxyl residue in membrane-bound pyrophosphatase of Rhodospirillum rubrum. 1992

I Romero, and H Celis

Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F.

Chemical modifications with water-soluble carbodiimides (EDC and CMC) were performed to elucidate whether some carboxyl residues are involved in the catalytic activity of membrane-bound pyrophosphatase of Rhodospirillum rubrum. EDC and CMC cause a loss of hydrolytic activity following pseudo-first-order kinetics up to 10 min of reaction. The enzyme was completely protected against EDC inhibition by PPi or Mg2+, whereas PPi or Mg2+ gave partial protection against CMC inactivation. Mg-PPi protected completely against the inhibition caused by both carbodiimides. These data suggest that the carboxyl moiety modified by EDC is at the active site. At longer times of inactivation with both carbodiimides, we could not observe a linear relationship in semilogarithmic plots of residual activity versus time, indicating that at least two carboxyls are involved in the inactivation, which correlates with the partial protection against CMC inactivation by PPi. We found that the activator site for Mg2+ is apparently at or near the active site of the enzyme. This is supported by the fact that PPi protects completely the activator effect of this divalent cation.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D011755	Pyrophosphatases	A group of enzymes within the class EC 3.6.1.- that catalyze the hydrolysis of diphosphate bonds, chiefly in nucleoside di- and triphosphates. They may liberate either a mono- or diphosphate. EC 3.6.1.-.	Pyrophosphatase
D011756	Diphosphates	Inorganic salts of phosphoric acid that contain two phosphate groups.	Diphosphate,Pyrophosphate Analog,Pyrophosphates,Pyrophosphate Analogs,Analog, Pyrophosphate
D002234	Carbodiimides	Compounds with the general formula RN	Carbodiimide
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D003028	CME-Carbodiimide		4-(2-((Cyclohexylimidocarbonyl)amino)ethyl)-4-methylmorpholinium,CME Carbodiimide,CMEC,Carbodiimide, CME
D003432	Cross-Linking Reagents	Reagents with two reactive groups, usually at opposite ends of the molecule, that are capable of reacting with and thereby forming bridges between side chains of amino acids in proteins; the locations of naturally reactive areas within proteins can thereby be identified; may also be used for other macromolecules, like glycoproteins, nucleic acids, or other.	Bifunctional Reagent,Bifunctional Reagents,Cross Linking Reagent,Crosslinking Reagent,Cross Linking Reagents,Crosslinking Reagents,Linking Reagent, Cross,Linking Reagents, Cross,Reagent, Bifunctional,Reagent, Cross Linking,Reagent, Crosslinking,Reagents, Bifunctional,Reagents, Cross Linking,Reagents, Cross-Linking,Reagents, Crosslinking
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D005022	Ethyldimethylaminopropyl Carbodiimide	Carbodiimide cross-linking reagent.	1-Ethyl-3-(3-Dimethylaminopropyl)Carbodiimide,3-(3-Dimethylaminopropyl)-1-Ethylcarbodiimide,EDAP-Carbodiimide,Carbodiimide, Ethyldimethylaminopropyl,EDAP Carbodiimide