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Cysteine protease

Cysteine Peptidase
Papain enzyme.png
Crystal structure of the cysteine peptidase papain in complex with its covalent inhibitor E-64. Rendered from PDB 1PE6
Identifiers
Symbol Peptidase_C1
Pfam PF00112
Pfam clan CL0125
InterPro IPR000668
SMART SM00645
PROSITE PDOC00126
MEROPS C1
SCOP 1aec
SUPERFAMILY 1aec
OPM superfamily 420
OPM protein 1m6d

Cysteine proteases, also known as thiol proteases, are enzymes that degrade proteins. These proteases share a common catalytic mechanism that involves a nucleophilic cysteine thiol in a catalytic triad or dyad.

Cysteine proteases are commonly encountered in fruits including the papaya, pineapple, fig and kiwifruit. The proportion of protease tends to be higher when the fruit is unripe. In fact, dozens of latices of different plant families are known to contain cysteine proteases. Cysteine proteases are used as an ingredient in meat tenderizers.

The MEROPS protease classification system counts 14 superfamilies plus several currently unassigned families (as of 2013) each containing many families. Each superfamily uses the catalytic triad or dyad in a different protein fold and so represent convergent evolution of the catalytic mechanism.

For superfamilies, P = superfamily containing a mixture of nucleophile class families, C = purely cysteine proteases. superfamily. Within each superfamily, families are designated by their catalytic nucleophile (C = cysteine proteases).

Families of Cysteine proteases


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