Gamma-Butyrobetaine Hydroxylase (gBBH)

Gamma-butyrobetaine dioxygenase catalyzes the formation of L-carnitine from gamma-butyrobetaine, the last step in the L-carnitine biosynthetic pathway. Carnitine is essential for the transport of activated fatty acids across the mitochondrial membrane during mitochondrial beta-oxidation.The predicted 387-amino acid human protein exhibited gamma-BBH activity when expressed in yeast. Northern blot analysis revealed that gamma-BBH is expressed as an approximately 1.7-kb mRNA at high levels in kidney, at moderate levels in liver, and at low levels in brain. No expression was detected in other tissues. The authors noted that this expression pattern is consistent with previous studies that found that gamma-BBH enzyme activity is high in kidney, moderate in liver, and low in brain.