Formation of β-hydroxyisovalerate by an α-ketoisocaproate oxygenase in human liver

Previously we demonstrated the occurrence of a soluble dioxygenase in rat liver which converts alpha-ketoisocaproic acid (the keto acid analog of leucine) to beta-hydroxyisovaleric acid. Herein we show that human liver contains a similar soluble enzyme which converts alpha-ketoisocaproate to beta-hydroxisovaleric acid. We suggest this enzyme functions as a "safety valve" in liver to help prevent excessive accumulation of alpha-ketoisocaproate.