Abstract: According to the present invention, there can be provided a novel polypeptide having ?1,3-galactosyltransferase activity involved in the synthesis of type 1 sugar chains, a DNA coding for said polypeptide, a recombinant vector comprising said DNA, a transformant carrying said recombinant vector, a process for producing type 1 sugar chain-containing sugar chains and complex carbohydrates by use of said polypeptide or said transformant, an antibody recognizing said polypeptide, a method for detecting or quantifying said polypeptide by use of said antibody, a method for screening a substance correlated with said polypeptide, a method for diagnosis or treatment of cancers in the digestive system by use of said DNA or said antibody, and a method for treatment of cancers in the digestive system by use of a substance obtained by said screening method.