Maize shoot cell walls under cadmium stress.

The composition of shoot cell walls of two maize hybrids (Zea mays L.), the sensitive Novania and the tolerant Almansa, both after cadmium treatment was studied. Previous results showed a smaller effect of cadmium on shoot physiological parameters (e.

Glucuronoxylan recognition by GH 30 xylanases: A study with enzyme and substrate variants.

XynA from Erwinia chrysanthemi (EcXyn30A), belonging to glycoside hydrolase family 30 subfamily 8, is specialized for hydrolysis of 4-O-methylglucuronoxylan (GX). Carboxyl group of 4-O-methylglucuronic acid serves as a substrate recognition element interacting ionically with positively charged Arg293 of the enzyme. We determined kinetic parameters of EcXyn30A on GX, its methyl ester (GXE) and 4-O-methylglucoxylan (GXR) and compared them with behavior of the enzyme variant in which Arg293 was replaced by Ala.

Impact of cadmium stress on two maize hybrids.

Some physiological parameters and composition of the root cell walls of two maize hybrids (monocots), the sensitive Novania and the tolerant Almansa were studied after treatment with cadmium cations. After 10 days of Cd treatment (1 × 10 M and 5 × 10 M), plant growth inhibition, in the sensitive hybrid in particular, as well as a certain alteration in root structure and pigment content were observed. The Cd accumulation was ten times higher in the roots than in the shoots.

Preparation and characterization of cationic and amphoteric mannans from Candida albicans.

Cationic and amphoteric mannans from Candida albicans were prepared by chemical modification with (3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHPTAC) and sodium chloroacetate under aqueous alkaline conditions. The optimal reaction conditions for mannan cationization were found to be 6h, 60°C, and NaOH/CHPTAC ratio of 1.0.

Glucuronoyl esterases are active on the polymeric substrate methyl esterified glucuronoxylan.

Alkali extracted beechwood glucuronoxylan methyl ester prepared by esterification of 4-O-methyl-D-glucuronic acid side residues by methanol was found to serve as substrate of microbial glucuronoyl esterases from Ruminococcus flavefaciens, Schizophyllum commune and Trichoderma reesei. The enzymatic deesterification was monitored by (1)H NMR spectroscopy and evaluated on the basis of the decrease of the signal of the ester methyl group and increase of the signal of methanol. The results show for the first time the action of enzymes on polymeric substrate, which imitates more closely the natural substrate in plant cell walls than the low molecular mass artificial substrates used up to present.