PEROXISOMAL D-HYDROXYACYL-COA DEHYDROGENASE-DEFICIENCY - RESOLUTION OF THE ENZYME DEFECT AND ITS MOLECULAR-BASIS IN BIFUNCTIONAL PROTEIN-DEFICIENCY

Peroxisomes play an essential role in a number of different metabolic pathways, including the beta-oxidation of a distinct set of fatty acid s and fatty acid derivatives. The importance of the peroxisomal beta-o xidation system in humans is made apparent by the existence of a group of inherited diseases in which peroxisomal beta-oxidation is impaired , This includes X-linked adrenoleukodystrophy and other disorders with a defined defect. On the other hand, many patients have been describe d with a defect in peroxisomal beta-oxidation of unknown etiology, Res olution of the defects in these patients requires the elucidation of t he enzymatic organization of the peroxisomal beta-oxidation system, Im portantly, a new peroxisomal beta-oxidation enzyme was recently descri bed called D-bifunctional protein with enoyl-CoA hydratase and 3-hydro xyacyl-CoA dehydrogenase activity primarily reacting with alpha-methyl fatty acids like pristanic acid and di- and trihydroxycholestanoic ac id. In this patient we describe the First case of D-bifunctional prote in deficiency as resolved by enzyme activity measurements and mutation analysis, The mutation found (Gly(16)Ser) is in the dehydrogenase cod ing part of the gene in an important loop of the Rossman fold forming the NAD(+)-binding site. The results show that the newly identified D- bifunctional protein plays an essential role in the peroxisomal beta-o xidation pathway that cannot be compensated for by the L-specific bifu nctional protein.