InterPro domain: IPR038492

Gamma-butyrobetaine hydroxylase (GBBH), also known as gamma-butyrobetaine dioxygenase, is a alpha-ketoglutarate-dependent dioxygenase that catalyzes the biosynthesis of L-carnitine by hydroxylation of gamma-butyrobetaine (GBB). GBBH is a dimeric enzyme. The monomer consists of a catalytic double-stranded beta-helix domain and a smaller N-terminal domain. The N-terminal domain has a bound Zn ion, which is coordinated by three cysteines and one histidine. The N-terminal domain could facilitate dimer formation, but its precise function is not known [ 1 ].

A related domain is found in another hydroxylase of the biosynthetic pathway of L-carnitive, the first enzyme of the pathway, known as trimethyllysine dioxygenase (TMLD). Like GBBH, TMLD is a non-heme ferrous-iron dioxygenase that requires alpha-ketoglutarate, Fe2+, and molecular oxygen as cofactors [ 2 ].

1. Crystal structure of human gamma-butyrobetaine hydroxylase. Biochem. Biophys. Res. Commun. 398, 634-9
2. Molecular and Biochemical Characterization of Rat epsilon -N-Trimethyllysine Hydroxylase, the First Enzyme of Carnitine Biosynthesis. J. Biol. Chem. 276, 33512-7