chemistry question

Simon Cross pcxsc at
Wed Sep 27 07:39:36 EST 2000

Arginine can be a nucleophile, but is not as good as lysine or maybe histidine.
It depends on the pH of your buffer - the pKa of residues can change from the
'norm' if in hydrophobic pockets, but if you try doing a pH profile of the
reaction you can see at which pH the guanidinium group of the arginine becomes
protonated and less nucleophilic which should stop the reaction. The chemistry
would probably be a straightforward SN2 displacement of the UDP by the
guanidinium nucleophile.Hope this is of some use,


Ivan Delgado wrote:

> Dear All,
>     Anybody has an idea what the chemistry of following reaction would be?:
> The glycosylation of an Arginine amino acid with the glucose from
> UDP-glucose.
>     I have a protein that can bind UDP-glucose and glycosylate itself at an
> Arginine and I am trying to figure out how this can take place.
>     Any ideas or a source of information regarding this question is
> appreciated.
>     Sincerely,
>     Ivan
> Ivan J. Delgado Orlic
> Graduate Student
> MSU-DOE-Plant Research Laboratory
> Genetics Department
> Michigan State University
> 178 Wilson Rd.
> 122 Plant Biology Building
> East Lansing, MI  48824-1312
> Email: delgadoi at
> URL:
> Phone: 517-353-3519
> FAX: 517-353-9168
> Francis Crick goes to heaven: "'God,' said the angel, 'This is Dr. Crick;
> Dr. Crick, this is God.' 'I am so pleased to meet you,' says Francis. 'I
> must ask you this question. How do imaginal disks work?'. "'Well,' comes the
> reply, 'We took a little bit of this stuff and we added some things to it
> and... actually, we don't know, but I can tell you that we've been building
> flies up here for 200 million years and we have had no complaints.'"
> -Dr. Sydney Brenner, NYT March 7, 2000
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