| Property | Human GALT summary |
|---|---|
| Gene symbol | **GALT** (galactose-1-phosphate uridylyltransferase), matching UniProt P07902 protein description (pqac-00000002, pqac-00000017) |
| UniProt ID | **P07902** (user-specified target; protein identity consistent with cited GALT literature) |
| EC number | **EC 2.7.7.12** galactose-1-phosphate uridylyltransferase (pqac-00000002, pqac-00000003) |
| Chromosomal location | **9p13.3** / 9p13 region in human genome (pqac-00000017, pqac-00000018) |
| Gene size and exons | ~**4.3 kb**, **11 exons** (pqac-00000017, pqac-00000018) |
| Protein length | **379 amino acids** per monomer (pqac-00000001, pqac-00000017) |
| Active form | **Homodimer** with **two active sites** contributed by both subunits (pqac-00000001, pqac-00000008, pqac-00000017) |
| Molecular mass | Active dimer ~**88 kDa**; GALT monomer detected at ~**43 kDa** in cell studies (pqac-00000017, pqac-00000025) |
| Protein family / superfamily | Member of the **galactose-1-phosphate uridylyltransferase family** and **HIT (histidine triad) superfamily** (pqac-00000000, pqac-00000007) |
| Key active-site residues | Conserved **His-Pro-His / histidine-triad** catalytic motif; catalytic nucleophile **His166** forms covalent UMP intermediate; active-site contribution from **H186** residues of both subunits; zinc-binding residues **E202, H301, H319, H321** stabilize structure/activity (pqac-00000001, pqac-00000007, pqac-00000008) |
| Catalytic mechanism | **Ping-pong double-displacement** mechanism with a covalent uridylylated enzyme intermediate and overall retention of configuration via two inversions (pqac-00000001, pqac-00000007) |
| Substrates | **Galactose-1-phosphate (Gal-1-P)** and **UDP-glucose (UDP-Glc)** (pqac-00000002, pqac-00000024) |
| Products | **Glucose-1-phosphate (Glc-1-P)** and **UDP-galactose (UDP-Gal)** (pqac-00000002, pqac-00000024) |
| Subcellular localization | **Cytosol / cytosolic UDP-Gal biosynthetic machinery** (directly supported by recent cell studies) (pqac-00000020, pqac-00000025) |
| Pathway | Central enzyme of the **Leloir pathway**: GALM → GALK1 → **GALT** → GALE, linking galactose catabolism to UDP-sugar metabolism (pqac-00000002, pqac-00000003, pqac-00000004) |
| Disease association | Deficiency causes **classic galactosemia (Type I)**, the most severe common galactosemia; acute neonatal disease and long-term neurologic/reproductive complications are characteristic (pqac-00000009, pqac-00000011, pqac-00000012) |


*Table: This table summarizes the core molecular, biochemical, structural, and disease-related properties of human GALT relevant for functional annotation. It provides a compact reference linking canonical gene/protein features to pathway role and clinical significance.*