CLONING AND CHARACTERIZATION OF A CDNA-ENCODING CHICKEN LIVER ALPHA-N-ACETYLGALACTOSAMINIDASE

Chicken liver alpha-N-acetylgalactosaminidase (alpha AGA) specifically removes terminally alpha-linked alpha-N-acetylgalactosamine from oligosaccharide chains on the surface of group A erythrocytes. Here, we report the molecular cloning of a alpha AGA cDNA by both library screening and PCR amplification. The clone contains a 1.2-kb 3'-untranslated region and 1.2-kb coding region which encodes a 45-kDa protein. The protein was produced in bacteria and in rabbit reticulocyte lysate, and is specifically recognized on Western blot by an antibody raised against the purified chicken liver enzyme. Enzymatic activity was detected when alpha AGA was produced in Saccharomyces cerevisiae. The deduced amino acid sequence shows 80% homology with human alpha AGA and about 60% homology with a-galactosidases from a number of sources, indicating that these two families of exoglycosidases are evolutionarily related.