Enzymic Degradation of Cereal Hemigelluloses Ii. Pattern of Pentosan Degradation

Abstract

Using water‐soluble araboxylan of rye as substrate, it is shown that enzymic degradation involves four enzymes or enzyme systems: (a) arabinosidase, liberating free arabinose from araboxylan and from oligosaccharides; (b) endoxylanase, degrading xylan chains, whether or not these carry arabinose side chains; (c) exoxylanase, producing xylobiose from araboxylan and from oligosaccharides after some degree of arabinose removal has been achieved; and (d) xylobiase, liberating free xylose from xylobiose and, perhaps, also from xylotriose. The first detectable low‐molecular product of the joint action of these enzymes is arabinose; xylobiose and xylose appear in detectable quantities somewhat later, and higher oligosaccharides later still. Oligosaccharides with back‐bone chains of up to six xylose residues have been observed, these carrying varying proportions of arabinose residues in side chains. Different raw cereals carry all four enzyme systems, but in different proportions; the malting enhancement of pentosanase activity in barley is small compared with the enhancement of β‐glucanase activity.

A Water-soluble Arabinogalactan-Peptide From Wheat Endosperm

“…This procedure differed from that of Kundig and co-workers in that human salivary amylase was substituted for porcine pancreatic amylase Table 1. Procedures for extraction of water-soluble polysaccbarides Method 1 based on the method of Kundig et al (1961) and method 2 on that of Preece and MacDougall (1958) and after starch digestion the amylase was removed by heat denaturation rather than by trichloroacetic acid precipitation. The use of trichloroacetic acid was avoided to minimize possible chemical degradation (e.g.…”

“…A single sample prepared by this procedure was used throughout and is.referred to as preparation A. The second procedure (method 2, Table 1) was based on the original method of Preece and MacDougall (1958). Although there was some variation in the protein content of different samples prepared by this method, their monosaccharide compositions were almost identical.'…”

“…As indicated in Table 2, the protein content of preparation B varied between 2 and 5 %, high values being found in large-scale preparations. Preece and MacKenzie (1952) in their initial work on the water-soluble polysaccharides from barley emphasized that the products obtained were free from contamination by nitrogenous material, and in subsequent papers (Preece and Hobkirk 1953;Preece and MacDougall 1958) no mention was made of protein associated with the polysaccharides extracted from cereal grains. The amino acid compositions of the proteins in preparation A and a sample of preparation B containing 2 % protein are shown in Table 3.…”

Identification and Characterization of a Novel Arabinoxylanase from Wheat Flour

“…NSP-hydrolyzing enzymes are found in wheat grain (Preece and MacDougall, 1958;Kulp, 1968;Lee and Ronalds, 1972;Schmitz et al, 1974;Bremen, 1981; Adlung, 1985;Moore and Hoseney, 1990), in germinated wheat and wheat bran (Beldman et al, 1996), in barley (Hordeum vulgure) aleurone layers (Taiz and Honigman, 1976;Dashek …”

“…NSP-hydrolyzing enzymes are found in wheat grain (Preece and MacDougall, 1958;Kulp, 1968;Lee and Ronalds, 1972;Schmitz et al, 1974;Bremen, 1981;Adlung, 1985;Moore and Hoseney, 1990), in germinated wheat and wheat bran (Beldman et al, 1996), in barley (Hordeum vulgure) aleurone layers (Taiz and Honigman, 1976;Dashek and Chrispeels, 1977;Benjavongkulchai and Spencer, 19861, and in germinated barley (Slade et al, 1989). Recently, evidence was presented for the presence of NSPhydrolyzing enzymes in wheat flour (Cleemput et al, 1995a(Cleemput et al, , 1995b.…”