A tale of two pectins: Diverse fine structures can result from identical processive PME treatments on similar high DM subtrates

Authors: OWEN, JESSIE - Massey University; KENT, LISA - Massey University; RALET, MARIE-CHRISTINE - Institut National De La Recherche Agronomique (INRA); Cameron, Randall - Randy; WILLIAMS, MARTIN - Massey University

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2017
Publication Date: 7/15/2017
Citation: Owen, J., Kent, L., Ralet, M., Cameron, R.G., Williams, M. 2017. A tale of two pectins: Diverse fine structures can result from identical processive PME treatments on similar high DM subtrates. Carbohydrate Polymers. 168:365-373.

Interpretive Summary: Pectin functionality is closely tied to the distribution of charge in its dominant molecular region. Charge distribution can be manipulated using a pectin modifying enzyme (pectin-methylesterase). We compared the effect of two of these enzyme's activity on two different pectin substrates. Both contained a very high amount of methyl esters in this dominant region that result in a more neutral molecule. We discovered that very different charge properties can be introduced depending on the starting substrate. We also learned that the resulting distribution of charge after enzyme treatment can enable us to discriminate between different starting substrates. We also determined that for enzymes of unknown mode of action the way they work can be determined by looking at how they change the charge distribution in a pectin molecule.

Technical Abstract: The effects of a processive pectin-methylesterase treatment on two different pectins, both possessing a high degree of methylesterification, were investigated. While the starting samples were purportedly very similar in fine structure, and even though the sample-averaged degree of methylesterifications of the treated samples generated were controlled to be the same, the intermolecular degree of methylesterification distributions arising from their pectin-methylesterase treatments were strikingly different. Herein, these experiments and the development of a simulation that illuminates the origin of this phenomenon are described. It is concluded that: 1) very different low-degree of methylesterification samples (with the same average degree of methylesterification) can be generated using the same processive pectin-methylesterase, simply by a judicious choice of the high degree of methylesterification starting material; 2) observing the intermolecular degree of methylesterification distribution of the products of processive-pectin-methylesterase-processing is an extremely sensitive discriminator of the fine structure of high degree of methylesterification starting materials; and 3) for pectin-methylesterases with unknown action patterns the processive nature of the enzyme is most simply revealed by studying the changes it induces in the intermolecular degree of methylesterification distribution of an initially very-highly-methylesterifed homogalacturonan.