histo-blood group ABO system transferase; NAGAT; glycoprotein-fucosylgalactoside alpha-N-acetylgalactosaminyltransferase; fucosylglycoprotein alpha-N-acetylgalactosaminyltransferase; histo-blood group A transferase; A transferase; glycoprotein-fucosylgalactoside alpha-galactosyltransferase; fucosylglycoprotein 3-alpha-galactosyltransferase; histo-blood group B transferase; B transferase (ABO)

Function

• basis of the ABO blood group system
• protein modification; protein glycosylation
• soluble form derives from the membrane form by proteolytic processing

UDP-N-acetyl-D-galactosamine + glycoprotein-alpha-L- fucosyl-(1->2)-D-galactose
        <-->
UDP + glycoprotein-N-acetyl-alpha-D-galactosaminyl-(1->3)- (alpha-L-fucosyl-(1->2))-D-galactose

UDP-galactose + alpha-L-fucosyl-(1->2)-D-galactosyl-R
            <-->
UDP + alpha-D-galactosyl-(1->3)-(alpha-L-fucosyl-(1->2))- D-galactosyl-R

Cofactor: binds 1 Mn+2 per subunit

Structure

• conserved DXD motif is involved in cofactor binding
• Mn+2 interacts with the beta-phosphate group of UDP & may also have a role in catalysis
• belongs to the glycosyltransferase 6 family

Compartment

• Golgi apparatus, Golgi stack membrane
• membrane-bound form in trans cisternae of Golgi
• secreted into the body fluid

Polymorphism

• B form differs from A form by a few residues
• O phenotype results from a single base frameshift in the N-terminal extremity of the gene, resulting in a severely truncated protein without catalytic activity

More general terms

• galactosyltransferase

Database

• OMIM: https://mirror.omim.org/entry/110300
• UniProt: http://www.uniprot.org/uniprot/P16442.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=28