Abstract
Branched chain alpha-ketoacid dehydrogenase (BCKAD) is located on the mitochondrial inner membrane and oxidatively decarboxy-lates the branched chain alpha ketoacids. It is presumably a multienzyme complex whose function is impaired in the inherited disorder Maple Syrup Urine Disease. However, neither the sub-unit composition nor the defective component in Maple Syrup Urine Disease has been identified. We have partially purified BCKAD from bovine liver mitochondria. It decarboxylates all 3 branched chain alpha ketoacids, has a maximum MW of 2.0 × 106 and minimum MW of 2.5 × 105 Daltons. It exhibits a typical flavoprotein spectra, and will reduce oxidized lipoamide with NADH as a substrate. To characterize this lipoamide dehydrogenase (LAD) immunologically, antibodies were produced against porcine LAD in rabbits and isolated by ion exchange chromatography. The monospecific IgG fraction completely inhibited porcine LAD activity at a 64:1 ratio. On Ouchterlony double diffusion gels a single precipitant band of identity was found between the porcine LAD and bovine BCKAD. We conclude that LAD is the flavoprotein subunit of the BCKAD multienzyme complex. The specific antibody to LAD can now be used to identify genetic defects in BCKAD and other mitochondrial dehydrogenase complexes. (Supported by NIH H.D. 08388)
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
