Effect of D42N substitution in Escherichia coli inorganic pyrophosphatase on catalytic activity and Mg2+ binding. 1996

S M Avaeva, and E V Rodina, and S A Kurilova, and T I Nazarova, and N N Vorobyeva
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russian Federation.

Asp-42 located in the active site of E. coli inorganic pyrophosphatase (PPase) has been substituted by Asn by site-directed mutagenesis. This resulted in a 3-fold increase in hydrolytic activity measured under optimal conditions, a 15.5-fold increase in the Km value and retention of the pK values of groups for enzyme and enzyme-substrate complex. The active site of the enzyme contains 4 metal binding centers (I-IV) [Harutyunyan et al. (1996) Eur. J. Biochem., in press]. Asp-42 is located near centers II and IV. The D42N replacement had no effect on Mg2+ binding with center II. At the same time, occupation of center IV eliminates the inhibition of inorganic pyrophosphate hydrolysis by high Mg2+ concentrations typical of wild-type PPase. It is proposed that the increase in activity and decrease in affinity for substrate of the D42N PPase results from changes in Mg2+ binding to center IV. The Mg2+ binding centers of E. coli PPase are lined up in filling order.

UI MeSH Term Description Entries
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
D002384 Catalysis The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction. Catalyses
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D005459 Fluorides Inorganic salts of hydrofluoric acid, HF, in which the fluorine atom is in the -1 oxidation state. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Sodium and stannous salts are commonly used in dentifrices. Fluoride
D006868 Hydrolysis The process of cleaving a chemical compound by the addition of a molecule of water.
D001216 Asparagine A non-essential amino acid that is involved in the metabolic control of cell functions in nerve and brain tissue. It is biosynthesized from ASPARTIC ACID and AMMONIA by asparagine synthetase. (From Concise Encyclopedia Biochemistry and Molecular Biology, 3rd ed) L-Asparagine
D001224 Aspartic Acid One of the non-essential amino acids commonly occurring in the L-form. It is found in animals and plants, especially in sugar cane and sugar beets. It may be a neurotransmitter. (+-)-Aspartic Acid,(R,S)-Aspartic Acid,Ammonium Aspartate,Aspartate,Aspartate Magnesium Hydrochloride,Aspartic Acid, Ammonium Salt,Aspartic Acid, Calcium Salt,Aspartic Acid, Dipotassium Salt,Aspartic Acid, Disodium Salt,Aspartic Acid, Hydrobromide,Aspartic Acid, Hydrochloride,Aspartic Acid, Magnesium (1:1) Salt, Hydrochloride, Trihydrate,Aspartic Acid, Magnesium (2:1) Salt,Aspartic Acid, Magnesium-Potassium (2:1:2) Salt,Aspartic Acid, Monopotassium Salt,Aspartic Acid, Monosodium Salt,Aspartic Acid, Potassium Salt,Aspartic Acid, Sodium Salt,Calcium Aspartate,Dipotassium Aspartate,Disodium Aspartate,L-Aspartate,L-Aspartic Acid,Magnesiocard,Magnesium Aspartate,Mg-5-Longoral,Monopotassium Aspartate,Monosodium Aspartate,Potassium Aspartate,Sodium Aspartate,Aspartate, Ammonium,Aspartate, Calcium,Aspartate, Dipotassium,Aspartate, Disodium,Aspartate, Magnesium,Aspartate, Monopotassium,Aspartate, Monosodium,Aspartate, Potassium,Aspartate, Sodium,L Aspartate,L Aspartic Acid
D013379 Substrate Specificity A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D016297 Mutagenesis, Site-Directed Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion. Mutagenesis, Oligonucleotide-Directed,Mutagenesis, Site-Specific,Oligonucleotide-Directed Mutagenesis,Site-Directed Mutagenesis,Site-Specific Mutagenesis,Mutageneses, Oligonucleotide-Directed,Mutageneses, Site-Directed,Mutageneses, Site-Specific,Mutagenesis, Oligonucleotide Directed,Mutagenesis, Site Directed,Mutagenesis, Site Specific,Oligonucleotide Directed Mutagenesis,Oligonucleotide-Directed Mutageneses,Site Directed Mutagenesis,Site Specific Mutagenesis,Site-Directed Mutageneses,Site-Specific Mutageneses

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