Porphyran Primary Structure

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Abstract
Porphyran, a highly substituted agarose from Porphyra umbilicalis, was degraded by highly purified .beta.-agarose I from Pseudomonas atlantica. This enzyme cleaved at the reducing side of units of .beta.-neoagarobiose (3,6-anhydro-.alpha.-L-galactopyranosyl-(1 .fwdarw. 3)-.beta.-D-galactopyranose). The oligosaccharides were divided into fractions of low and high MW by dialysis. The permeate (23% of total starting carbohydrate) was separated by ion-exchange into neutral and anionic fractions. Gel filtration of the neutral fraction (19%) resolved 2 major oligosaccharides. These were shown by 13C-NMR spectroscopy to be 63-O-methyl-neoagarotetraose and 63,65-di-O-methyl-neoagarohexose. Gel filtration of the anionic oligosaccharides (3.3%) revealed 2 novel monosulfated tetrasaccharides, 6-O-sulfato-.alpha.-L-galactopyranosyl-(1 .fwdarw. 3)-.beta.-D-galactopyranosyl-(1 .fwdarw. 4)-3,6-anhydro-.alpha.-L-galactopyranosyl-(1 .fwdarw. 3)-D-galactopyranose and its 63-O-methylated derivative. The 13C-NMR data from the sulfated tetrasaccharides provided a novel reference which was used to characterize higher, partially sulfated fragments in the dialysis permeate. The fraction retained on dialysis (77%) had an average degree of polyermization of 40 and was homologous with the high MW anionic permeate. From 13C-NMR spectroscopy porphyran was comprised of 49% sulfated disaccharide units which occur in stretches averaging 2.0-2.5 contiguous units.