Papain, 100g

Papain is a sulfhydryl protease from Carica papaya latex. (A second protease, chymopapain, and a lysozyme have also been isolated from this same source.) Since native crystalline papain is quite unreactive until acted upon by mild reducing agents such as cysteine or cyanide, it may exist as a zymogen. Papain is widely used in cell isolation. With some tissues papain has proved less damaging and more effective than other proteases. Of the enzymes used for dissociating turtle retina, papain produced the least trauma. Intact single photoreceptor cells have also been isolated from adult salamander retina with papain. Papain used to obtain high yields of viable, morphologically intact cortical neurons from postnatal rats. Used for dissociation of postnatal rat hippocampus. Papain is used with fetal as well as postnatal brain regions to provide maximal dissociation and viability of neurons. It is also used to produce Fab fragments of antibodies. In addition, papain is used in red cell serology to modify the red cell surface to enhance or destroy the reactivity of many red cell antigens. Papain is useful for platelet serology studies. Papain has also been used in the enzymatic synthesis of amino acids, peptides, and other molecules. Papain is a cysteine protease that cleaves peptide bonds of basic amino acids, leucine, or glycine. It is also hydrolyzes esters and amides. Papain consists of a single polypeptide chain with three disulfide bridges and a sulfhydryl group necessary for activity of the enzyme.