3615-55-2Relevant articles and documents
Reversal of the substrate specificity of CMP N-glycosidase to dCMP
Sikowitz, Megan D.,Cooper, Lisa E.,Begley, Tadhg P.,Kaminski, Pierre Alexandre,Ealick, Steven E.
, p. 4037 - 4047 (2013/07/27)
MilB is a CMP hydrolase involved in the early steps of biosynthesis of the antifungal compound mildiomycin. An enzyme from the bacimethrin biosynthetic pathway, BcmB, is closely related to MilB in both sequence and function. These two enzymes belong to the nucleoside 2′-deoxyribosyltransferase (NDT) superfamily. NDTs catalyze N-glycosidic bond cleavage of 2′- deoxynucleosides via a covalent 2-deoxyribosyl-enzyme intermediate. Conservation of key active site residues suggests that members of the NDT superfamily share a common mechanism; however, the enzymes differ in their substrate preferences. Substrates vary in the type of nucleobase, the presence or absence of a 2′-hydroxyl group, and the presence or absence of a 5′-phosphate group. We have determined the structures of MilB and BcmB and compared them to previously determined structures of NDT superfamily members. The comparisons reveal how these enzymes differentiate between ribosyl and deoxyribosyl nucleotides or nucleosides and among different nucleobases. The 1.6 A structure of the MilB-CMP complex reveals an active site feature that is not obvious from comparisons of sequence alone. MilB and BcmB that prefer substrates containing 2′-ribosyl groups have a phenylalanine positioned in the active site, whereas NDT family members with a preference for 2′-deoxyribosyl groups have a tyrosine residue. Further studies show that the phenylalanine is critical for the specificity of MilB and BcmB toward CMP, and mutation of this phenylalanine residue to tyrosine results in a 1000-fold reversal of substrate specificity from CMP to dCMP.
FURANOSE RING ANOMERIZATION: A KINETIC STUDY OF THE 5-DEOXYPENTOSES AND 5-O-METHYLPENTOSES
Snyder, Joseph R.,Serianni, Anthony S.
, p. 13 - 26 (2007/10/02)
The anomerzation of 5-deoxy-L-pentoses (1-4) and 5-O-methyl-D-pentoses (5-8) in aqueous solution has been studied by (13)C saturation-transfer n.m.r. (s.t.-n.m.r.) spectroscopy, using compounds substituted with (13)C at the anomeric carbon atom.Unidirectional rate-constants of ring-opening (kopen) and ring closing (kclose) have been obtained for these compounds under identical solution conditions (50mM acetate buffer, pH 4.0 at 60 deg C), and have been compared to those measured for the D-tetroses (9 and 10) and four D-pentose 5-phosphates (11-14).Based on these comparisons, several correlations between furanose structure and reactivity have been revealed, and models have been proposed to explain the observed kinetic behavior of compounds 1-10.The effect of exocyclic structure on acid-catalyzed rate-constants was also examined by comparing the behavior of 5-deoxy-L-lyxose and 5-O-methyl-D-lyxose.Some consideration has been given to identifying the factors (enthalpic and entropic) that may play roles in determining the effect of structure on anomerization reactivity.
Ion exchange purification of ribose-5-phosphate.
GROTH,MUELLER,LEPAGE
, p. 389 - 391 (2007/12/04)
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