View source for Papain

It is a [[cysteine hydrolase|cysteine hydrolase]] that is stable and active under a awide range of conditions. It is very stable even at elevated temperatures <ref>Cohen, L., Coghlan, V and Dihel, L. (1986) Cloning and Sequencing of papain-encoding cDna, Gene 48, 219, 1986</ref>. The [[latex|latex]] of ''[[Carica papaya|Carica papaya]]'' is a rich source of four [[cysteine endopeptidases|cysteine endopeptidases]] including papain, [[chymopapain|chymopapain]], [[glycyl endopeptidase|glycyl endopeptidase]], and [[caricain|caricain]]. The proteins are synthesized as inactive precursors that become active with two minutes of the plant being wounded and the latex expelled. Papain is a minor constituent, but has been more widely studied because it is more easily purified <ref>Akahane, K. and Umeyama,H. (1986) Binding Specificity of Papain and Cathepepsin B, Emzyme 36, 141</ref>.<br> 

=== Molecular Weight:  ===

*23.4 kDa (theoretical) 
*23.0 kDa&nbsp;<ref>Drenth, J., Jansonius, J. Koekoek,R., Swen, H., and Wolters, B.(1968) Structure of Papain, Nature 218, 929</ref><br>

=== Active site residies:  ===

*[[cysteine|cysteine]] (c158) 
*[[histidine|histidine]] (h292) 
*[[asparagine|asparagine]] (n308)<br>

=== Applications:  ===

*Cell isolation where it is more gentle than other [[proteases|proteases]] (i.e. [[cortical neurons|cortical neurons]], [[retina|retina]], and [[smooth muscle|smooth muscle]]) 
*Protein structural studies, peptide mapping 
*[[Red cells|Red cell]] surface modification for antibody screening or identification 
*Fab preparation from [[IgG|IgG]] and [[IgM|IgM]] [[Antibody|antibodies]]
*Solubilization of integral membrane proteins 
*Production of [[glycopeptides|glycopeptides]] from purified [[proteoglycans|proteoglycans]]
*Enzymatic wound debridement<br>

=== References ===

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