Carbohydrase and sulphatase activities of Porphyra umbilicalis

Abstract

A qualitative investigation has been made of some enzymes present in extracts of the red seaweed Porphyra umbilicalis, particular attention being paid to those which catalyse reactions involving derivatives and polymers of galactose. The principal low-molecula.r-weight carbohydrates of the alga have been isolated since they were potential substrates for the enzyme system. These were floridoside and isofloridoside. It is concluded that in the seaweed samples examined in the present study, the isofloridoside component is 1-O-[alpha]-D-galactopyranosyl-D-glycerol. Porphyra umbilicalis extracts exhibit many of the carbohydrase activities previously reported for other algal extracts, namely [alpha]- and [beta]-glucosidase, amylase, [beta]-glucanase and mannanase. An [alpha]-galactosidase activity is also present for which floridoside is possibly the natural substrate. Some implications of this, in terms of the carbohydrate metabolism of the seaweed, are discussed. At least two enzymes having action on porphyran, the principal component of the plant, are present. One of these is a sulphatase which is inhibited by citrate, and the other catalyses a reaction causing a fall in the viscosity of the polysaccharide solution.