ARS | Publication request: CHARACTERIZATION OF THE TYPE 1 PECTIN METHYLESTERASE PURIFIED FROM VALENCIAORANGE PEEL

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2002
Publication Date: March 27, 2002
Citation: Journal of Agricultural and Food Chemistry. 2002. V.50, No. 12. p3553-3558.

Interpretive Summary: Enormous domestic reserves of pectin ($5-8/pound) could be produced from the by-products of fruit juice and sugar beet sugar processing that are now used for cattle feed (cents/pound). The majority of all pectin currently sold in the U.S. is imported. Chemical treatments have been used to modify pectin's gelling properties which can degrade the pectin decreasing its quality as a gum. We developed an enzymatic method to modify pectin's gelling properties without decreasing its gum quality. The research in this report describes a citrus enzyme, called pectin methylesterase, that was purified from a commercial enzyme preparation and found to be identical to the major pectin methylesterase in Valencia orange peel based on biochemical properties. Finally, we demonstrate that this enzyme acts in a blockwise action pattern that will improve pectin's gum properties in food and industrial chemical products. The development of new food and industrial chemical markets for pectin will add value to domestic fruit an vegetable crops benefitting producers and processors.

Technical Abstract: The pectin methylesterase (EC 3.1.1.11) available in a commercial orange peel enzyme preparation was characterized to establish its identity among the multiple isoforms present in mature Valencia orange (Citrus sinensis L.) peel. We show this enzyme corresponds to the peak 2 pectin methylesterase previously separated by heparin-Sepharose chromatography (Cameron et al., J Food Sci 63:253, 1998). This identification is based o common elution profiles of purified enzymes using perfusion chromatography on various cation-exchange and hydrophobic-interaction columns and by their identical molecular weight and pI by SDS- and IEF-PAGE. The commercial orange peel PME and Valencia peak 2 PME are also shown to share common biochemical properties, including a broad pH activity range and activity in the absence of supplemented cations. All evidence presented is consistent with classifying this orange peel PME as a type 1 isoform.