کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2029332 1070555 2011 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Substrate specificity and inhibitor analyses of human steroid 5β-reductase (AKR1D1)
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Substrate specificity and inhibitor analyses of human steroid 5β-reductase (AKR1D1)
چکیده انگلیسی

Human steroid 5β-reductase (aldo-keto reductase 1D1) catalyzes the stereospecific NADPH-dependent reduction of the C4–C5 double bond of Δ4-ketosteroids to yield an A/B cis-ring junction. This cis-configuration is crucial for bile acid biosynthesis and plays important roles in steroid metabolism. The biochemical properties of the enzyme have not been thoroughly studied and conflicting data have been reported, partially due to the lack of highly homogeneous protein. In the present study, we systematically determined the substrate specificity of homogeneous human recombinant AKR1D1 using C18, C19, C21, and C27 Δ4-ketosteroids and assessed the pH-rate dependence of the enzyme. Our results show that AKR1D1 proficiently reduced all the steroids tested at physiological pH, indicating AKR1D1 is the only enzyme necessary for all the 5β-steroid metabolites present in humans. Substrate inhibition was observed with C18 to C21 steroids provided that the C11 position was unsubstituted. This structure activity relationship can be explained by the existence of a small alternative substrate binding pocket revealed by the AKR1D1 crystal structure. Non-steroidal anti-inflammatory drugs which are potent inhibitors of the related AKR1C enzymes do not inhibit AKR1D1. By contrast chenodeoxycholate and ursodeoxycholate were found to be potent non-competitive inhibitors suggesting that bile-acids may regulate their own synthesis at the level of AKR1D1 inhibition.

Research highlights
► AKR1D1 proficiently catalyzes the 5β-reduction of a series of Δ4-3-ketosteroids.
► Bile-acids are potent non-competitive inhibitors of AKR1D1 and may regulate their own synthesis via this mechanism.
► AKR1D1 is the only enzyme required to account for the spectrum of 5β-reduced steroids in humans.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Steroids - Volume 76, Issue 5, April 2011, Pages 484–490
نویسندگان
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