Circadian Rhythm of the Enzymes Participating in the CO2-Photoassimilation of a Brown Alga, Spatoglossum pacificum

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Abstract
Diurnal changes in the activities of enzymes taking part in the CO2 photoassimilation of a brown alga, S. pacificum, were investigated. The activities of RuDP [ribulose diphosphate] carboxylase [EC 4.1.1.39], aldolase [EC 4.1.2.13], FDPase [fructose diphosphate phosphohydrolase EC 3.1.3.11] and mannitol-1-phosphate 1-phosphohydrolase [EC 3.1.3.-; M1Pase] which catalyze the individual reaction steps of mannitol biosynthesis, showed the rhythm patterns of a day type, while the rhythm patterns of acid phosphatase and R5P [ribulose-5-phosphate] isomerase [EC 5.3.1.6], which participate indirectly in this photoassimilation, were of an intermediate and of a night type, respectively. When the alga was cultured in a continuous light or dark or under reversed day and night conditions, wave lengths of the rhythm patterns of these enzyme activities showed a tendency to shorten to various extents depending on the modification of light or dark culture conditions.