Aspartic acid residue location

Trypsin hydrolysis of SR vesicles cleaves the (Ca2, Mg2+)-ATPase into three fragments, NH2-20 000, 30 000 and 45 OOO-COOH. The phosphorylation site is associated with an aspartic acid residue in the 30 000 fragment and ionophoric activity with the 20 000 fragment. The amino terminus of the enzyme is located on the cytoplasmic side of the membrane.143... 

The different specificities of the proteolytic enzymes are due to specificity pockets at the binding site (Fig. 15-8). These pockets on the surface of the enzyme accommodate the side-chain of the amino acid residue located on the carbonyl side of the scissile bond of the substrate. In trypsin, a serine residue present in chymotrypsin is replaced by an aspartate residue. This allows the binding of cationic arginine and lysine residues instead of bulky aromatic side chains. In elastase, two glycine residues of chymotrypsin are replaced by valine and threonine. Their bulky side chains block the specificity pocket so that elastase hydrolyzes peptide bonds adjacent to smaller, uncharged side chains. 

Ohnuma S, Narita K, Nakazawa T, Ishida C, Takeuchi Y, Ohto C, Nishino T (1996) A role of the amino acid residue located on the fifth position before the first aspartate-rich motif of famesyl diphosphate synthase on determination of the final product. J Biol Chem 271 30748-30754... 

Acylphosphate formation is characteristic for P-type ATPases and involves the transfer of the y-phosphate of ATP to an aspartic acid residue to form a high-energy enzyme intermediate. The phosphorylated aspartic acid residue is located in the sequence DKTGT, which is universally conserved in all members of the P-type superfamily. By this criterion, CopA and CopB of En. hirae are clearly members of the P-type superfamily of ATPases and probably function by the same underlying mechanism. Vanadate sensitivity is another hallmark of P-type ATPases. CopA and CopB were inhibited by vanadate with /50 values of around 0.1 mM. This is a low vanadate sensitivity compared to /50 values in the micromolar to submicromolar range observed for non-heavy metal P-type ATPases. 

Figure 1 Chemical mechanism of DNA polymerase and 3 -5 exonuclease, (a) DNA polymerase reaction. The enzyme chelates two metal Ions using three aspartic acid residues (only two are shown). Metal ion A abstracts the 3 hydroxyl proton of the primer terminus to generate a nucleophile that attacks the a-phosphate of an incoming dNTP substrate. The phosphoryl transfer results In production of a pyrophosphate leaving group, which is stabilized by metal Ion B. (b) The 3 -5 exonuclease proofreading activity is located in a site that is distinct from the polymerase site yet it uses two-metal-ion chemistry similar to DNA synthesis. The reaction type is hydrolysis in which metal ion A activates water to form the hydroxy anion nucleophile. Nucleophile attack on the phosphate of the mismatched nucleotide releases it as dNMP (dGMP in the case shown).

Several pharmaceutical enzymes belong to the group of serine-histidine estero-proteolytic enzymes (serine proteases), which display their catalytic activity with the aid of an especially reactive serine residue, whose (3-hydroxyl group forms a covalent bond with the substrate molecule. This reaction takes place by cooperation with the imidazole base of histidine. The specificity of the enzymes is achieved by the characteristic structure of their substrate-binding centers, which in these proteases are built according to the same principle. They consist of a hydrophobic slit formed by apolar side chains of amino acids and a dissociated side chain-located carboxyl group of an aspartic acid residue at the bottom. 

Fig. 2 BACE-1 characteristics. The overall fold of BACE-1 is typical for an aspartic acid protease, consisting of an N- and C-terminal lobe with the substrate binding site located in a crevice between the two lobes [99, 100], A flexible hairpin, called the flap (Yellow see-through surface), partially covers the active site of BACE-1 and can adopt many different conformations as a result of inhibitor binding. In the center of the active site are the two aspartic acid residues orange and inset) that are involved in the enzymatic reaction... 

The WPD loop is a flexible /3-turn found in all tyrosine-specific PTPs, and includes the conserved aspartic acid residue that serves as a general acid-base catalyst. Substrate binding thermodynamically favors the closed, catalytically active conformation, where the aspartic acid is in position for catalysis (Figure 15). The DSPs also share a conserved aspartic acid in this catalytic role. However, except for VHZ, a recently purified DSP which may possess a flexible IPD loop, the aspartic acid in DSPs is located on a rigid structure. Consequently, no conformational change analogous to WPD loop movement in PTPs seems to be associated with catalysis for most DSPs. 

Effect of Different Pentamer Sequence Arrangements of the Same 30-mer Composition. Chemically synthesized polytricosapeptides, poly (30-mers), were prepared with compositions of 1 aspartic acid residue (Asp, D) and 5 more-hydrophobic phenylalanine (Phe, F) residues replacing valine (Val, V) residues per repeat of 30 residues, but with different relative locations of D and F residues. These compositions are written ... 

Sequence determinations show that two catalytically active aspartic acid residues are located in highly conservative surroundings,... 

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