Sandbox 33

From Proteopedia

Introduction

, also known as papaya proteinase I, is a in papaya (Carica papaya) and mountain papaya (Vasconcellea cundinamarcensis)^[1]. Papain is present in the leaves, latex, roots and fruit of the papaya plant ^[2]. The latex of Carica papaya is a rich source of four cysteine endopeptidases including papain, chymopapain, glycyl endopeptidase, and caricain. The proteins are synthesized as inactive precursors that become active within two minutes of the plant being wounded and the latex expelled. Papain is a minor constituent, but it has been more widely studies because it is more easily purified ^[3].

History

Papain was first named in the late nineteenth century by Wurtz and Bouchut who partially purified the product from the sap of papaya. When named, it was simply recognized as proteolytically active constituent in the latex of tropical papaya fruit. Throughout the mid 1950's and 1960's, purification and separation techniques improved greatly and pure papain was isolated. The study of papain allowed for great advances in understanding enzymes as proteins. In 1968, papin was the second enzyme to be crystallized and its structure determined by X-ray methods. Papain was the first cysteine protease to have its structure identified. In the 1980's, the geometry of the was reviewed and the three-dimensional structure was determined to a 1.65 Angstrom resolution. The precursors and inhibitors of papain were extensively studied into the 1990's. Today's research aims to further understand the specificity and structural perturbations brought about by inhibitors, low pH, metal ions, and fluorinated alcohols^[4].

Structure

Papain is a single-chained polypeptide with three and a sulfhydryl group necessary for the activity of the enzyme. It is a sulfhydryl protease from the latex of the papaya fruit. Its molecules consist of one polypeptide chain with 212 amino acid residues. The chain is folded into with the in a groove between the domains.

Extraction

Papain