Final answer:
Papain cleaves IgG antibodies into Fab and Fc fragments, where the Fab retains antigen binding capacity while the Fc part does not bind antigens but crystallizes easily.
Step-by-step explanation:
When papain is added to a solution of antibodies, particularly IgG molecules, it acts as an enzyme that cleaves the antibodies into two fragments. The first fragment, termed Fab (fragment of antigen binding), retains the ability to bind to antigens. The second fragment, known as Fc (fragment crystallizable), does not bind antigens but can crystallize easily. Each of these fragments has a molecular weight of about 50,000 Daltons, with the Fab accounting for approximately two-thirds and the Fc for one-third of the digested IgG molecule. Furthermore, papain can be used in fragment-based methods to discover selective irreversible covalent inhibitors of cysteine proteases, serving as a model cysteine-dependent enzyme.