Enzyme systems for fragmentation of the rhamnogalacturonan sites main chains in plant tissue protopectin complex

Abstract

Special features of the protopectin complex structure of plant tissue suggest the necessity of performing point destruction of certain glycoside bonds in the structure of rhamnogalacturonan polymer chains for industrial production of pectin. These chains include homogalacturonan sites and branching zones. As the homogalacturonan fragments of the protopectin complex carry the main functional load, glycoside bonds between residues of rhamnose and galacturonic acid are targeted bonds. For their directional destruction, it is most expedient to use enzymes of lyase and hydrolase action. The aim of this review is to systemize notions of molecular specific features of enzymes of lyase and hydrolase action that catalyze the process of enzymatic destruction of the rhamnogalacturonan main chain. The paper examines systematics of lyase and hydrolase enzymes by mechanism of destruction of glycoside bonds and by molecular structure. It is shown that the classification data intercross, as a result, each family can include one or several enzyme groups. The review shows the main structural difference of enzymes of lyase and hydrolase action that consists in the obligatory presence of Ca2+ cations in the composition of lyase enzymes. These cations take part in stabilization of conformation of the enzyme molecule and in the catalytic process per se blocking the residue of galacturonic acid. Ca2+ cations are absent in the composition of targeted hydrolase enzymes. Molecular specific features of lyase enzymes determine sensitivity of their catalytic activity to the presence of Ca2+ cations in the system. Exceeding certain concentration can lead to the antagonistic effect. There is no unambiguous idea of this regarding hydrolase enzymes. The review demonstrates the necessity of studying approaches to assessment of expediency of preliminary partial removal of cations from the substrate.