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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOACTIVE CONSTITUENTS AND SPECIALTY FOOD FIBERS AS VALUE-ADDED PRODUCTS FROM CITRUS PROCESSING WASTE

Location: Citrus and Other Subtropical Products Research

Title: Purification and characterization of a papaya (Carica papaya L.) pectin methylesterase isolated from a commercial papain preparation

Authors
item Vasu, Prasanna -
item Savary, Brett -
item Cameron, Randall

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 16, 2012
Publication Date: January 24, 2012
Citation: Vasu, P., Savary, B.J., Cameron, R.G. 2012. Purification and characterization of a papaya (Carica papaya L.) pectin methylesterase isolated from a commercial papain preparation. Food Chemistry. 133:366-372.

Interpretive Summary: A commercially available extract obtained from papaya trees contains an enzyme that modifies the pectin backbone. We have purified this enzyme from the extract and characterized its physical and chemical properties. We have also described fragments of the enzyme that will enable others to determine if it is present in their materials. We have shown that it is capable of modifying the functional properties of pectin.

Technical Abstract: We purified a single stable pectin methylesterase (CpL-PME; EC 3.1.1.11) from a commercial papain preparation, which is isolated from Carica papaya (L.) fruit latex. This CpL-PME was separated from the abundant cysteine endopeptidases activities using sequential hydrophobic interaction and cation-exchange chromatographies and then purified by affinity chromatography with the kiwi PME inhibitor protein to obtain an electrophoretically homogeneous protein. The enzyme was purified 92-fold with 38% yield, providing a specific activity of 1,200 U/mg. The molecular weight determined by MALDI-TOF MS was 35,135, and peptide mass fingerprinting by trypsin digestion provided a large set of peptide ions for identifying the protein. The CpL-PME required salt for activity; it showed a broad pH range of 6-9 and moderate thermostability (optimum ca. 70 degrees C); and it readily converted a methylated citrus pectin to high calcium sensitivity with -6% deesterfication. These properties support further research to apply CpL-PME to tailor pectin nanostructure.

Last Modified: 7/24/2014