glycogen debranching enzyme; glycogen debrancher [includes: 4-alpha-glucanotransferase, oligo-1,4-1,4-glucantransferase; amylo-alpha-1,6-glucosidase, amylo-1,6-glucosidase, dextrin 6-alpha-D-glucosidase] (AGL, GDE)

Function

• multifunctional enzyme in glycogen degradation
  • transferase activity 1,4-alpha-D-glucan:1,4-alpha-D-glucan 4-alpha-D-glycosyl- transferase
  • glucosidase activity amylo-1,6-glucosidase in glycogen degradation
• transfers a segment of a 1,4-alpha-D-glucan to a new position in an acceptor, which may be glucose or a 1,4-alpha-D-glucan
• hydrolysis of (1->6)-alpha-D-glucosidic branch
• linkages in glycogen phosphorylase limit dextrin

Structure

• monomer
• products of the mRNAs termed isoforms 1 to 4 are identical
• N-terminus is blocked
• belongs to the glycogen debranching enzyme family

Alternative splicing

named isoforms=3

Expression

• liver, kidney & lymphoblastoid cells express predominantly isoform 1
• muscle & heart express not only isoform 1, but also muscle-specific isoform mRNAs (isoforms 2, 3 & 4).
• isoforms 5 & 6 are present in both liver & muscle

Pathology

• defects in AGL are the cause of glycogen storage disease type 3

Laboratory

• AGL gene mutation
• amylo-alpha-1,6-glucosidase in leukocytes

More general terms

• glucosidase
• hexosyltransferase

Database

• OMIM: https://mirror.omim.org/entry/232400
• UniProt: http://www.uniprot.org/uniprot/P35573.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=178