A. Caravano et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1123–1125
1125
HO
HO
O
O
OH
O
OH
HO
HO
HO
+ UDP + UGM
O
O
HO
UDP
OH
UDP-Galf
HO
O
OH
1
UDP
UDP-Galp
Figure 2. Conditions of the enzymatic assays: pH 7.3, T = 21 °C, reducing ([Na2SO4] = 20 mM, reaction times up to 3 h) and non-reducing
conditions (reaction times up to 5 days), [UDP] 200 lM–1 mM, [1] 500 lM–5 M, [UGM] 40 nM–4 lM.
cofactor.19 The Km values of UDP-Galf are 20 lM and
190 lM under reducing or non-reducing (native) condi-
tions, respectively. UGM is thus much more kinetically
competent upon dithionite addition. Moreover, the
binding modes of nucleotide-sugars with UGM have
also been shown to vary when the flavin is reduced.14,20
Under both conditions (reducing or not), we never ob-
served the formation of UDP-galactose when UGM
was incubated with 1 and UDP.
´ ´ ´ `
Delegue a la Recherche et aux Nouvelles Technologies
(PhD grant to A.C.).
References and notes
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Acknowledgments
This work was supported by the Centre National de la
`
Recherche Scientifique (CNRS) and by the Ministere
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