Cysteine-dependent aspartate specific

At the molecular level, apoptosis is tightly regulated and is mainly orchestrated by the activation of caspases [24], Caspases, or cystein-dependent aspartate-specific proteases, are a family of cysteine proteases which have... 

Many elements of complex intrinsic and extrinsic signaling pathways leading to apoptosis have been identified. During apoptosis, a cascade of proteases termed caspases is involved with upstream signaling events and downstream executioner events. Caspases are cysteine-dependent, aspartate-specific proteases that contain highly conserved cysteine residues in their active sites and cleave substrates leaving C terminal Asp residues. Caspase-3 is one of the main effector molecules of the apoptotic process. It cleaves several target proteins and serves as one of the executioner caspases that implement apoptosis. Despite reports of caspase-independent apoptosis (Broker et al. 2005), caspase-3 has become the most widely accepted and most frequently measured apoptosis marker for HTS. 

CASPASE Cysteine-dependent aspartate-specific protease... 

A family of specialized proteases, named caspases, is central to the apoptotic program (review Griitter, 2000). The name caspase is a contraction of cysteine-dependent, aspartate-specific protease. These proteases use a Cys residue as a nucleophile and cleave the substrate after an Asp residue. The only known eukaryotic proteases with this specificity are the caspases themselves and the cytotoxic serine protease granzyme B from T-lymphocytes. 

It is noteworthy that there is another limiting factor in the choice of amino acid types at the junction sites which affect the enzymatic process of the intein. For example, in the case of SceVMA (also called PI-Seel) from the IMPACT system, proline, cysteine, asparagine, aspartic acid, and arginine cannot be at the C-terminus of the N-terminal target protein just before the intein sequence. The presence of these residues at this position would either slow down the N-S acyl shift dramatically or lead to immediate hydrolysis of the product from the N-S acyl shift [66]. The compatibility of amino acid types at the proximal sites depends on the specific inteins and needs to be carefully considered during the design of the required expression vectors. The specific amino acid requirements at a particular splicing site depends on the specific intein used and is thus a crucial point in this approach. 

For some time, the endoproteases Lys-C, Glu-C, and Arg-C have also been used. Lys-C cleaves specifically at the carboxyl terminal side of lysine residues and still works in 5 M urea or 0.1% SDS. Glu-C cleaves at the carboxyl terminal side of glutamate or aspartate residues, depending on the buffer. Arg-C is a cysteine protease that cleaves peptide bindings at the carboxyl terminal side of arginine residues. 

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