کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
8290076 1536338 2014 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A pre-steady state and steady state kinetic analysis of the N-ribosyl hydrolase activity of hCD157
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
A pre-steady state and steady state kinetic analysis of the N-ribosyl hydrolase activity of hCD157
چکیده انگلیسی
hCD157 catalyzes the hydrolysis of nicotinamide riboside (NR) and nicotinic acid riboside (NAR). The release of nicotinamide or nicotinic acid from NR or NAR was confirmed by spectrophotometric, HPLC and NMR analyses. hCD157 is inactivated by a mechanism-based inhibitor, 2′-deoxy-2′-fluoro-nicotinamide arabinoside (fNR). Modification of the enzyme during the catalytic cycle by NR, NAR, or fNR increased the intrinsic protein fluorescence by approximately 50%. Pre-steady state and steady state data were used to derive a minimal kinetic scheme for the hydrolysis of NR. After initial complex formation a reversible step (360 and 30 s−1) is followed by a slow irreversible step (0.1 s−1) that defined the rate limiting step, or kcat. The calculated KMapp value for NR in the hydrolytic reaction is 6 nM. The values of the kinetic constants suggest that one biological function of cell-surface hCD157 is to bind and slowly hydrolyze NR, possibly converting it to a ligand-activated receptor. Differences in substrate preference between hCD157 and hCD38 were rationalized through a comparison of the crystal structures of the two proteins. This comparison identified several residues in hCD157 (F108 and F173) that can potentially hinder the binding of dinucleotide substrates (NAD+).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 564, 15 December 2014, Pages 156-163
نویسندگان
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