Pathway of mannitol formation during photosynthesis in brown algae<xref ref-type="fn" rid="fn1"><sup>1</sup></xref>

Abstract

Eisenia bicyclis, Arame, was allowed to photosynthesize in seawater containing H14CO3−, and 14C-mannitol was isolated from its fronds. The ratio of 14C-total/14C1 + 14C6 in the 14C-mannitol was found to be about 8.0 at 1 min-illumination, but gradually decreased with time to 3.0, showing uniform radioactivity distribution. Mannitol therefore seems to be formed in brown algae through three carbon compounds. Enzymes which may be involved in the possible biosynthetic pathway of mannitol, i.e. aldolase, hexose diphosphatase, mannitol-1-phosphatase and glucosephosphate isomerase were present in extracts from several brown algae. Some of their properties are discussed.