Human brain short chain L-3-hydroxyacyl coenzyme A dehydrogenase is a single-domain multifunctional enzyme. Characterization of a novel 17beta-hydroxysteroid dehydrogenase.
Human brain short chain L-3-hydroxyacyl-CoA dehydrogenase ( SCHAD) was found to catalyze the oxidation of 17beta-estradiol and dihydroandrosterone as well as alcohols. Mitochondria have been demonstrated to be the proper location of this NAD+-dependent dehydrogenase in cells, although its primary structure is identical to an amyloid beta-peptide binding protein reportedly associated with the endoplasmic reticulum (ERAB). This fatty acid beta-oxidation enzyme was identified as a novel 17beta-hydroxysteroid dehydrogenase responsible for the inactivation of sex steroid hormones. The catalytic rate constant of the purified enzyme was estimated to be 0.66 min-1 with apparent Km values of 43 and 50 microM for 17beta-estradiol and NAD+, respectively. The catalytic efficiency of this enzyme for the oxidation of 17beta-estradiol was comparable with that of peroxisomal 17beta-hydroxysteroid dehydrogenase type 4. As a result, the human SCHAD gene product, a single-domain multifunctional enzyme, appears to function in two different pathways of lipid metabolism. Because the catalytic functions of human brain short chain L-3-hydroxyacyl-CoA dehydrogenase could weaken the protective effects of estrogen and generate aldehydes in neurons, it is proposed that a high concentration of this enzyme in brain is a potential risk factor for Alzheimer's disease.[1]References
- Human brain short chain L-3-hydroxyacyl coenzyme A dehydrogenase is a single-domain multifunctional enzyme. Characterization of a novel 17beta-hydroxysteroid dehydrogenase. He, X.Y., Merz, G., Mehta, P., Schulz, H., Yang, S.Y. J. Biol. Chem. (1999) [Pubmed]
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