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A proton wire to couple aminoacyl-tRNA
A proton wire to couple aminoacyl-tRNA

Purine and pyrimidi..
Purine and pyrimidi..

... Purine bases (guanine, hypoxanthine and adenine) resulting during purine catabolism, may not complete the degradation to give uric acid, but react with PRPP again to resynthesize purine nucleotides. This occurs in some organs in which de no vo synthesis can not takes place e.g. in brain and RBCs. Th ...
Protonation States and pKa
Protonation States and pKa

... The positively charged amino group attached to the acarbon helps to push the departing proton of the carboxyl group out more easily. The inflection point pI is the point when removal of the first proton is complete and he second has just begun so the amino acid’s prevalent form is as a dipolar ion ...
UNITED `STATES` PATENT
UNITED `STATES` PATENT

... disodium glutamate as the neutralizing agent, 25 stantial part of the dehydrated composition at a in amounts such that together they are equiv particular pH which isgmore alkaline than that alent to the monosodium glutamate of the stand in which the food is customarily consumed. It is ard mix descri ...
Citric Acid Cycle
Citric Acid Cycle

... Why is citric acid cycle so important? Citric acid cycle is of central importance in all living cells that use oxygen as part of cellular respiration. In aerobic organisms, the citric acid cycle is part of a metabolic pathway involved in the chemical conversion of carbohydrates, fats and proteins i ...
Tangping Li, Ke Fan, Jun Wang and Wei Wang Reduction of protein
Tangping Li, Ke Fan, Jun Wang and Wei Wang Reduction of protein

... as (Ile, Ala, Glu, Lys, Gly), which coincide with the experimental results of the 57 residue SH3 domain by Baker and coworkers (Riddle et al., 1997). (Hereafter, the residues are simply represented as single letters.) One of the advantages of such a reduction is that it reduces greatly the complexit ...
papain, a plant enzyme of biological importance
papain, a plant enzyme of biological importance

Chapter 17. Amino Acid Oxidation and the Production of Urea
Chapter 17. Amino Acid Oxidation and the Production of Urea

... other transformations of amino acids • Different aminotransferases (e.g., aspartate and alanine aminotransferases), each catalyzes the transfer of the amino group from an amino acid to a-ketoglutarate to form Glu and a a-keto acid. • Pyridoxal phosphate (PLP), being derived from vitamin B6 (i.e., py ...
Enzymes lII: Clinical Applications
Enzymes lII: Clinical Applications

... Serum is used for many enzyme assays because the preparation of plasma requires addition of anticoagulants (e.g., chelating agents) that interfere with some assays. Enzymes in circulating plasma are either plasma-specific or nonplasma-specific. Plasma-specific enzymes are normally present in plasma, ...
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... Five S-carboxymethy1cysteine-containing peptides from thermolytic digests of ovalbumin which had been reduced and S-carboxymethylated with [2- 14C]iodoacetic acid were isolated by paper ionophoresis and chromatography and their amino acid sequences determined. The two half-cystine residues involved ...
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... Formation of a double bond in a fatty acid involves the following endoplasmic reticulum membrane proteins in mammalian cells:  NADH-cyt b5 Reductase, a flavoprotein with FAD as prosthetic group.  Cytochrome b5, which may be a separate protein or a domain at one end of the desaturase.  Desaturase, ...
Threonine Metabolism via Two-carbon Compounds
Threonine Metabolism via Two-carbon Compounds

... had been grown initially on threonine medium. Good growth occurred on acetate alone. Growth on an equimolar mixture of acetate plus glycine took place without lag as rapidly as growth on threonine. No growth occurred on 2-oxobutyrate medium. Washed suspensions of Pse udomonas oxalaticus grown on L-t ...
BCHEM 253 – METABOLISM IN HEALTH AND DISEASES
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... The general acid catalyst protonating the carbonyl group is His-95. The result is the enediol intermediate. His-95 then functions as a general base abstracting the hydrogen from the hydroxyl group with Glu-165 functioning as a general acid donating its proton to the C2 carbon forming G-3-P. ...
Insect Biochemistry 15:
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... Abstract--Glutamine synthetase (GS) of fleshfly flight muscle was unstable in crude extracts, but could be stabilised by the reagents glutathione and MnCI2. The enzyme was purified to homogeneity and had a molecular weight of 324,000. Michaelis constants for the three substrates of the biosynthetic ...
Amino Acids Interp Guide
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... the basic constituents of all hormones, enzymes and neurotransmitters. Assessment of amino acid levels will help to identify contributors to illness and allow for precise replacement of deficient amino acids. Because various vitamins and minerals are used as cofactors in amino acid metabolism, imbal ...
Urea cycle
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... • Increased concentration of ammonia in the blood and other biological fluids → ammonia difuses into cells, across blood/brain barrier → increased synthesis of glutamate from -ketoglutarate, increased synthesis of glutamine  -ketoglutarate is depleted from CNS → inhibition of TCA cycle and produc ...
Poon, Andy: Predicting Phosphorylation: A critique of the NetPhos program and potential alternatives
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... The purpose of using quantitative pattern matching was to possibly identify known motifs common to phosphorylated proteins. Perhaps documented motifs existed, initially attributed to other protein features, which may be indicative of phosphorylation as well. (For instance, perhaps these databases r ...
Crystal structure of potato tuber ADP‐glucose pyrophosphorylase
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Chap. 3A Amino Acids, Peptides, and Proteins Topics Amino acids
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... The a-carboxyl and a-amino groups of all amino acids, along with the ionizable R groups of 7 amino acids, function as weak acids and bases in aqueous solutions (Table 3-1). The pKas of these functional groups depend on the chemical properties of the groups themselves and range between 1.8-2.4 for th ...
amino acids and proteins
amino acids and proteins

... associate with one another and remain isolated from water. • Amino acids in this group play an important role in maintaining the three dimensional structure of proteins. ...
Amino acid sequence and structural repeats in schistosome
Amino acid sequence and structural repeats in schistosome

... influence of bordering sequences (cf. e-tropomyosin). The coiled coil is stabilized by two types of interaction: non-polar and ionic. Nonpolar residues at positions a and d form a "core" of interlocking hydrophobic side chains. Charged groups, particularly those in positions e and g, can form intram ...
Chem*3560 Lecture 15: Gluconeogenesis
Chem*3560 Lecture 15: Gluconeogenesis

... reaction, because phosphoenolpyruvate (PEP) has an exceptionally high ∆ Go ' of hydrolysis (–61.9 kJ/mol). The strategy used is to add a carboxylate group to pyruvate first, which yields oxaloacetate. Since decarboxylation always releases considerable energy, an ATP must be used as an energy source ...
Purification and characterization of the 1-3
Purification and characterization of the 1-3

Topological studies suggest that the pathway of the protons through
Topological studies suggest that the pathway of the protons through

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Catalytic triad



A catalytic triad refers to the three amino acid residues that function together at the centre of the active site of some hydrolase and transferase enzymes (e.g. proteases, amidases, esterases, acylases, lipases and β-lactamases). An Acid-Base-Nucleophile triad is a common motif for generating a nucleophilic residue for covalent catalysis. The residues form a charge-relay network to polarise and activate the nucleophile, which attacks the substrate, forming a covalent intermediate which is then hydrolysed to regenerate free enzyme. The nucleophile is most commonly a serine or cysteine amino acid, but occasionally threonine. Because enzymes fold into complex three-dimensional structures, the residues of a catalytic triad can be far from each other along the amino-acid sequence (primary structure), however, they are brought close together in the final fold.As well as divergent evolution of function (and even the triad's nucleophile), catalytic triads show some of the best examples of convergent evolution. Chemical constraints on catalysis have led to the same catalytic solution independently evolving in at least 23 separate superfamilies. Their mechanism of action is consequently one of the best studied in biochemistry.
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