ABSTRACT

Dissolved proteinaceous materials in surface seawater in Funka Bay, Hokkaido, Japan were fractionated according to their molecular weight and analyzed for their amino acid composition by HPLC. Ultrafiltration membranes with different nominal cut-off sizes were used to fractionate the proteinaceous materials into molecular weight classes of approximately 500, 10, 000, and 100, 000 daltons. Amino acid content in the low molecular weight fraction (500 to 10, 000 daltons) accounted for 57 and 80% of the total amino acid contents in proteinaceous materials. The amino acid composition of this fraction was characterized by a relatively high abundance of cystine (10 to 15% of total amino acid content) during a spring bloom of phytoplankton. It was suggested that the high abundance of cystine in the fraction was caused by the spring bloom of diatom.