Isolation from papaya extracts

An essentially pure extracellular glycoprotein proteinase inhibitor was isolated from the latex of green fruits of papaya by a single affinity chromatography purification step. An immobilized trypsin-Sepharose CL 4B column was prepared according to the manufacturer (Amersham Pharmacia Biotech), which provided elaborated bulletins for the preparation procedures and applications of these affinity gel columns. Latex extract was applied to the column after equilibration with 20 mM Tris-HCl, pH 8.0, containing 0.5 M NaCl and 0.05 M CaCli. The column was extensively washed with the same buffer until ultraviolet (UV) absorbance became undetectible. The bound trypsin inhibitor was eluted with 0.02 M HCl and recovered by lyophilization after dialysis against water. 

Homologues of the classical papaya papain that have been tested for peptide S5mthesis are plant-derived enzymes such as bromelain and ficain. Bromelain extracted from pineapple could be applied in Met- and Leu-enkephalin synthesis in a low water system, reaching 97% yield [27]. Ficain isolated from Ficus glabrata latex was tested in di- and tripeptide synthesis in frozen water medium [23] and was used in the synthesis of Lys and Met oligomers starting from the respective ethyl esters [29]. 

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