Aspartic acid, characteristics

Lysine and aspartic acids are two of the amino acids found in proteins. Describe the acid-base characteristics of these compounds. 

Caspases are a family of evolutionary conserved cysteine proteases that cleave their substrates after an aspartic acid residue within a defined consensus sequence (Alnemri et al, 1996). They play a cracial role in the apoptotic program, as most of the characteristic features observed in apoptosis are attributable to their action (Eamshaw et al, 1999). They are... 

Cultures of Streptomyces rimosus var paromomycinus characteristically develop UV absorption at 240 and 278 nm due to formation of malonomicin (22), a compound that shows antiprotozoal activity towards Trypanosoma congolense, the causative agent of sleping sickness in cattle [42]. Malonomicin contains an unique aminomalonic acid unit that, on brief heating in water, undergoes decarboxylation and results in a compound devoid of biological activity [43]. Hydrolysis of the compound yielded L-serine and racemic aspartic acid. The structure was elucidated by chemical and spectroscopic methods [43,44] and was confirmed by total synthesis [45]. 

Aspartame. Aspartame is a widely used intense sweetener that has excellent taste characteristics, ft is a peptide made from two amino acids, phenylalanine and aspartic acid, but will in an acidic beverage medium slowly hydrolyse to its components. The fact that aspartame is a source of phenylalanine is of concern to consumers with certain complaints, and suitable label declarations are now required by law. Technically, this slow hydrolysis brings about loss of sweetness. 

Over 50% of the aspartic acid of the proteins of hepatic origin is liberated in 16 hours, but the gamma-globulins of extrahepatic origin required 36 hours to reach 50%. The extent to which this reflects certain characteristics of the primary structure is described in similar studies on insulin, ribonuclease, and glucagon (37). The cleavage of the peptide chain at the aspartic acid bonds may release other amino acids when they are between aspartic acid residues, when the aspartic acid is penultimate at either end of the chain, or if the other residues occupy positions of particularly labile sequences not known at this time. The... 

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. 

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