Syntheses of unnatural N-substituted UDP-galactosamines as alternative substrates for N-acetylgalactosaminyl transferases
摘要:
UDP-GalNAc analogues with slight modifications in the 2-acetamido group of the GalNAc moiety are prepared in order to study their role in the mechanism of the N-acetylgalactosaminyl transferase mediated glycosylation step. The analogues with N-propionyl, N-butyryl- and N-bromoacetyl-groups were synthesized, utilizing Khorana's morpholidate coupling method starting from D-galactosaminyl-l-phosphate after selective N-acylation of its amino group with the appropriate N-acyloxysuccinimides. Furthermore. in addition to UDP-galactosamine its 2-azido analogue has been efficiently prepared involving a metal catalyzed diazo transfer reaction. (C) 2002 Elsevier Science Ltd. All rights reserved.
Reduction of an Aldehyde by a NADH/Zn<sup>2+</sup>-Dependent Redox Active Ribozyme
作者:Shinya Tsukiji、Swetansu B. Pattnaik、Hiroaki Suga
DOI:10.1021/ja0495213
日期:2004.4.28
We report here the ability of an alcohol dehydrogenase (ADH) ribozyme to reduce a benzaldehyde. While the ribozyme was initially evolved in vitro based on the activity for the NAD+-dependent oxidation of the benzyl alcohol, we found that this ADH ribozyme is also capable of reducing the aldehyde in the presence of NADH and Zn2+. The rate acceleration gained by ribozyme catalysis was more than 6 orders of magnitude larger than the spontaneous reaction. Although the reversibility of phosphordiester and acyl transfer reactions catalyzed by ribozymes was known, that of other chemical reactions has not been well established. This study has demonstrated the reversibility of a hydride transfer chemistry catalyzed by the ADH ribozyme. Most interestingly, the ribozyme shares many features with the protein ADHs, e.g., reversibility and NADH/Zn2+ dependence.
Syntheses of unnatural N-substituted UDP-galactosamines as alternative substrates for N-acetylgalactosaminyl transferases
作者:Daniel Lazarevic、Joachim Thiem
DOI:10.1016/s0008-6215(02)00183-0
日期:2002.11
UDP-GalNAc analogues with slight modifications in the 2-acetamido group of the GalNAc moiety are prepared in order to study their role in the mechanism of the N-acetylgalactosaminyl transferase mediated glycosylation step. The analogues with N-propionyl, N-butyryl- and N-bromoacetyl-groups were synthesized, utilizing Khorana's morpholidate coupling method starting from D-galactosaminyl-l-phosphate after selective N-acylation of its amino group with the appropriate N-acyloxysuccinimides. Furthermore. in addition to UDP-galactosamine its 2-azido analogue has been efficiently prepared involving a metal catalyzed diazo transfer reaction. (C) 2002 Elsevier Science Ltd. All rights reserved.