β1,4-N-Acetylglucosaminyltransferase-IV (MGAT4) transfers GlcNAc toβ1-4 of mannose on the GlcNAcβ1-2Manα1-3 structure (GlcNAcβ1-2Manα1-3Manβ1-R) synthesized by MGAT1. MGAT4 does not have activity or affinity to the glycan structure received bisect GlcNac by MGAT3. MGAT4A, which has high homology to bovine enzymes, and MGAT4B, which has low homology to bovine enzymes, are known as MGAT4. MGAT4B was cloned from human genome. Both are characterized as similar optimal pH and Mn2+ concentration, but are different in cation dependency. Co2+ can activate MGAT4B comparably to that Mn2+ does.
This page does not indicate all of the enzymatic reaction, and expression of "MGAT4B".