Sandbox 33: Difference between revisions

Papain is a single-chained polypeptide with three <scene name='Sandbox_33/Disulfide_bonds_2/1'>disulfide bridges</scene> and a sulfhydryl group necessary for the activity of the enzyme as well as <scene name='Sandbox_33/Polar_and_nonpolar_residues/1'>polar and non-polar residues</scene>. Papain is a one-chain protein with the following <scene name='Sandbox_33/Secondary_structrues/1'>secondary structures</scene>: five alpha helices (pink) and seven beta sheets (orange). Papain is expressed as an inactive precursor, prepropapain. The papain precursor contains 345 amino acid residues, and consists of a signal sequence, a propeptide, and the mature peptide. The amino acid numbers are based on the mature peptide<ref>Worthington Biochemical Corporation. Worthington Enzyme Manual: Papain http://www.worthington-biochem.com/pap/default.html</ref>. The main chain consists of 212 amino acid residues. The chain is folded into two structural domains with the active site in a groove between the domains containing a catalytic diad. The catalytic diad is made up of the amino acids Cys 25 and His 159<ref>Wikipedia: The Free Encyclopedia http://en.wikipedia.org/wiki/Papain</ref>.