PURPOSE: To rapidly insolubilize the title marine protein useful as a biological adhesive without coloring by adding an oxidase, a crosslinking agent and ascorbic acid to a protein containing lysine and tyrosine.

CONSTITUTION: A marine protein containing lysine and tyrosine secreted from a hard-shelled mussel, etc., is incorporated with an oxidase (e.g. tyrosinase) and/or an organic crosslinking agent (e.g. glutaraldehyde) and L-ascorbic acid as a color protecting agent so that the protein containing lysine and tyrosine useful as a biological adhesive in vivo, etc., is insolubilized while suppressing coloring. The amount of L-ascorbic acid added is preferably 25-75mol% based on tyrosine residue and glyoxal, o-, m- or p-phthaladehyde, etc., may be used as the crosslinking agent besides glutaraldehyde.