Proteases are widely distributed in most of biological source (plant and animal sources). They are ubiquitous with wide diversity of sources such as plants and animals.

Plant Proteases
Papain, bromelain and ficin represent some of the well-known proteases of plant origin. Papain is a traditional plant protease and isolated from the latex of Carica papaya fruits. This enzyme is active between pH 5-9 and is stable up to 90°C. Bromelain is extracted from the stem and juice of pineapples. The enzyme is also called as cysteine protease which is less stable than that of papain. A neutral protease is alsopurified from Raphanus sativus leaves. An aspartic protease is also present in potato leaves with different physiological roles and Thiol Protease is also purified from Pineapple Crown Leaf. Serine protease was also found in artificially senescing parsley leaves whose proteolytic activity was found low in young leaves and increased from the start of senescence lead to reduction in the protein content of the leaves. Endoproteases were also isolated from alfalfa, oat and barley senesced leaves which are involved in the process of protein degradation during foliar senescence.

Animal Proteases
The most common proteases of animal origin are pancreatic trypsin, chymotrypsin, pepsin, and rennins. Trypsin is the main intestinal digestive enzyme which is responsible for the hydrolysis of food proteins. It is a type of serine protease and hydrolyzes peptide bonds in which the carboxyl groups are contributed by the lysine and arginine residues. Chymotrypsin is found in animal pancreatic extract and it is also expensive enzyme which is used only for diagnostic and analytical applications. It is specific for the hydrolysis of peptide bonds in which the carboxyl groups are provided by one of the three aromatic amino acids, i.e., phenylalanine, tyrosine, or tryptophan. It is used extensively in the de-allergenizing of milk protein hydrolysates. Pepsin is an acidic protease and present in the stomachs of vertebrates. Rennet is a pepsin-like protease (rennin, chymosin) which is present in its inactive precursor, pro-rennin, in the stomachs of all ruminants. It is used exclusively in the dairy industry to produce good flavored curd.

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Dr. Kirti Rani Sharma,
Assistant Professor (II),
Amity Institute of Biotechnology,
Amity University Uttar Pradesh, Noida
Sec-125, Gautam Buddha Nagar, Noida-201303 (UP), India.
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