Polygalacturonases (PGs) fine-tune pectins to modulate cell wall chemistry and mechanics, impacting plant development. The large number of PGs encoded in plant genomes leads to questions on the diversity and specificity of distinct isozymes. Herein, we report the crystal structures of two Arabidopsis thaliana polygalacturonases, POLYGALACTURONASE LATERAL ROOT (PGLR) and ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE2 (ADPG2), which are co-expressed during root development. We first determined the amino acid variations and steric clashes that explain the absence of inhibition of the plant PGs by endogenous PG-Inhibiting Proteins (PGIPs). Although their beta helix folds are highly similar, PGLR and ADPG2 subsites in the substrate-binding groove are occupied by divergent amino acids. By combining molecular dynamic simulations, analysis of enzyme kinetics and hydrolysis products, we showed that these structural differences translated into distinct enzyme-substrate dynamics and enzyme processivities: ADPG2 showed greater substrate fluctuations with hydrolysis products, oligogalacturonides (OGs), with a degree of polymerization (DP) of ≤4, while the DP of OGs generated by PGLR was between 5 and 9. Using the Arabidopsis root as a developmental model, exogenous application of purified enzymes showed that the highly processive ADPG2 had major effects on both root cell elongation and cell adhesion. This work highlights the importance of PG processivity on pectin degradation regulating plant development.

The risk of cardiovascular disease (CVD) is approximately doubled in subjects with hypercholesterolemia compared to those with normal blood cholesterol levels. Monacolin K (MK), the main active substance in rice fermented by the Monascus purpureus, acts on cholesterol metabolism. Rice also contains other bioactive compounds such as γ-oryzanol (OZ) and γ-aminobutyric acid (GABA). In a randomized, placebo-controlled, double-blind trial, the efficacy and tolerability of a food supplement (FS) based on an ingredient standardized to contain monacolins (4.5%), OZ, and GABA were evaluated in subjects with mild dyslipidemia. For the duration of the trial, enrolled subjects (n = 44, each group) received the FS or placebo and were instructed to use an isocaloric diet. Compared to the placebo group, after a 3 months of the FS, the mean low-density lipoprotein cholesterol and mean TC values were reduced by 19.3 and 8.3%, respectively, while the mean high-density lipoprotein cholesterol value increased by 29.3%. On average, the subjects shifted from very high to moderate CVD risk. Glucose metabolism and hepatic and renal parameters did not change after the treatment and no adverse events were reported. Guidelines to handle hypercholesterolemia with food supplements in specific clinical settings are needed to better manage mild dyslipidemia.