Cysteine Protease
Aspartic Acid
Catalytic Triad
The first step in the reaction mechanism by which cysteine proteases catalyze the hydrolysis of peptide bonds is deprotonation of a thiol in the enzyme's active site by an adjacent amino acid with a basic side chain, usually a histidine residue.
The next step is nucleophilic attack by the deprotonated cysteine's anionic sulfur on the substrate carbonyl carbon. In this step, a fragment of the substrate is released with an amine terminus, the histidine residue in the protease is restored to its deprotonated form, and a thioester intermediate linking the new carboxy-terminus of the substrate to the cysteine thiol is formed.
Therefore, they are also sometimes referred to as thiol proteases. The thioester bond is subsequently hydrolyzed to generate a carboxylic acid moiety on the remaining substrate fragment, while regenerating the free enzyme.
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https://en.m.wikipedia.org/wiki/Catalytic_triad
https://en.m.wikipedia.org/wiki/Aspartic_acid
https://en.m.wikipedia.org/wiki/Cysteine_protease
https://en.m.wikipedia.org/wiki/Serine
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Lectin
Papain
Mannan
Mannose
Mannitol
Polyol
Sugar Alcohol
Mannan-Binding Lectin (MBL)
Serine Proteases (MASPs)
Cysteine Protease
Lectin Binding
Calcium Binding
Mannans are polysaccharides that are linear polymers of the sugar mannose.
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Mannan-binding-lectin-associated serine proteases, characteristics and disease associations
https://pubmed.ncbi.nlm.nih.gov/16189649/
MASP-2 deficiency has been described as the result of a mutation causing the exchange of aspartic acid with a glycine at position 105, a position in the first domain, CUB1, involved in calcium binding. This mutation abolishes the binding to MBL and ficolins, and deprives MASP-2 of functional activity. The index case suffered from recurrent severe infections and autoimmune reactions.
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https://en.m.wikipedia.org/wiki/Mannans
https://en.m.wikipedia.org/wiki/Lectin_pathway
Studies on the inactivation of soluble and immobilized papain by the ascorbic acid-Cu2+ system: a model to propose the effect of free radicals on membrane-bound enzymes in vivo
RE: Carboxysome: Bacterial Microcompartment