Factory Supply High Quality Papaya Extract,China Huike price supplier
Factory Supply High Quality Papaya Extract
min.order / fob price
≥1 piece
OriginChina
Production Capacity5000Kg/Month
CategoryEnzymes
Update Time2025-08-23
company profile
Shaanxi Huike Botanical Development Ltd.
China
Contact: Ms.Kiki
Tel: 86-29-89565380
Number of Employees: 50 ~ 100
Business Type: Manufacture & Trade
product details
Model No:SHKM059
Standard:HQ
Origin:China
Brand:Huike
Papain, also known as papaya proteinase I, is a Cysteine protease (EC 3.4.22.2) enzyme present in papaya (Carica papaya) and mountain papaya (Vasconcellea cundinamarcensis).
The papain precursor protein contains 345 amino acid residues, and consists of a signal sequence (1-18), a propeptide (19-133) and the mature peptide (134-345). The amino acid numbers are based on the mature peptide. The protein is stabilised by three disulfide bridges. Its three-dimensional structure consists of two distinct structural domains with a cleft between them. This cleft contains the active site, which contains a catalytic diad that has been likened to the catalytic triad of chymotrypsin. The catalytic diad is made up of the amino acids - cysteine-25 (from which it gets its classification) and histidine-159. Aspartate-158 was thought to play a role analogous to the role of aspartate in the serine protease catalytic triad, but that has since then been disproved. Nonetheless, it does appear to play a role.
The mechanism by which it breaks peptide bonds involves deprotonation of Cys-25 by His-159. Asparagine-175 helps to orient the imidazole ring of His-159 to allow this deprotonation to take place. Cys-25 then performs a nucleophilic attack on the carbonyl carbon of a peptide backbone. This frees the amino terminal of the peptide, and forms a covalent acyl-enzyme intermediate. The enzyme is then deacylated by a water molecule, and releases the carboxy terminal portion of the peptide. In immunology, papain is known to cleave the Fc (crystallisable) portion of immunoglobulins (antibodies) from the Fab (antigen-binding) portion.