The red seaweed Pyropia yezoensis has been demonstrated to be a novel resource for the production of high-quality agar. P. yezoensis is grown for the food industry in large-scale Japanese mariculture operations. However, discolored P. yezoensis is mostly discarded as an industrial waste, although it has some kind of utility values. Here, we evaluated the utility of discolored P. yezoensis as a resource for agar production. The quality of agar from the discolored seaweed was comparable to that from normal seaweed. In addition, as a distinguishing characteristic, agar yield was higher from discolored seaweeds than from normal types. Moreover, we successfully used agar from discolored P. yezoensis for bacterial plate media and DNA electrophoresis gels without agarose purification. Thus, our results demonstrate that discolored P. yezoensis is suitable for agar production and use in life science research. Diverting discolored P. yezoensis from disposal to agar production provides a solution to the current industrial waste problem in mariculture, as well as a secure source of agar for research purposes.

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In order to determine the epitope of metallothionein (MT) to a murine monoclonal antibody (MT 189-14-7) which had been produced by immunization with rat MT 2 (Kikuchi et al. (1988) Mol. Immunol. 25, 1033-1036), various lengths of synthetic oligopeptides were tested for their inhibitory activities in competitive radioimmunoassay (RIA). The amino-terminal acetylated pentapeptide, AcMDPNC, exhibited an inhibitory activity comparable to that of native MTs, whereas the acetylated tetrapeptide, AcMDPN, and the deacetylated heptapeptide, MDPNCSC, were much less inhibitory. The results suggest that the major part of the epitope structure of MT to the MT 189-14-7 monoclonal antibody is located within the amino-terminal acetylated pentapeptide, AcMDPNC. The specificities of polyclonal rabbit anti-MT antisera raised against the same immunogen were also determined by using various animal MTs and synthetic peptides as inhibitors in the RIA. Among three antisera tested, two reacted with several amino-terminal oligopeptides similarly to the MT 189-14-7 antibody. The major epitope structures to these polyclonal antibodies were shown to be located within the acetylated tetrapeptide, AcMDPN. Another antiserum contained at least two different populations of antibodies: one consisted of antibodies reactive with the amino-terminal synthetic peptides, while the other was not reactive with them. These results suggest that, in the rabbit also, the amino-terminal region common to various animal MTs can be an epitope to antibodies raised against rat MT, as shown in the mouse. Moreover, the results indicate that the synthetic amino-terminal peptides are useful for determination of the specificity of polyclonal rabbit anti-MT antibodies, which have been widely used for the quantification of MTs.

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