May regulate the electrogenic sodium/bicarbonate cotransporter SLC4A4 activity and Mg(2+)-sensitivity. On the contrary of its homolog AHCYL1, does not regulate ITPR1 sensitivity to inositol 1,4,5-trisphosphate (PubMed:19220705). H2O + S-adenosyl-L-homocysteine = adenosine + L-homocysteine Binds 1 NAD(+) per subunit. Amino-acid biosynthesis; L-homocysteine biosynthesis; L-homocysteine from S-adenosyl-L-homocysteine: step 1/1. Homotetramer (Probable). Forms heteromultimers with AHCYL1 (via the C-terminal region) (PubMed:19220705). Interacts with ITPR1; with lower affinity than AHCYL1 and maybe via ITPR1 (PubMed:19220705). Interacts with SLC4A4 (By similarity). Interacts with ZCCHC4 (PubMed:31799605). Associates with membranes when phosphorylated, probably through interaction with ITPR1. Phosphorylated during neuronal differentiation at the LISN domain. Belongs to the adenosylhomocysteinase family. Extended N-terminus.