The structures of several enzymatic hydrolysis products of Nothogenia erinacea seaweed xylan, a linear homopolymer with mixed β-(1 → 3)/β-(1 → 4) linkages, were analysed by physicochemical and biochemical techniques. With the glycoside hydrolase family 10 β-(1 → 4)-xylanase from Cryptococcus adeliae, hydrolysis proceeds to a final mixture of products containing a mixed linkage-type triose as a major compound, whereas with the family 11 xylanase from Thermomyces lanuginosus this is a mixed linkage tetraose. The Cryptococcus xylanase is shown to be capable of also catalysing the hydrolysis of β-(1 → 3) linkages, that is this of a mixed type tetraose intermediary formed, in accordance with the broader substrate specificity of family 10 enzymes. From a partial degradation experiment with the T. lanuginosus xylanase, a series of higher mixed oligosaccharides were isolated and identified. The observed oligosaccharide intermediates and splicing pattern indicate an irregular β-(1 → 3)/β-(1 → 4) linkage distribution within the linear d-xylose polymer. Similar results were obtained with rhodymenan, the seaweed xylan from Palmares palmata. |
