[orgo814]

How is glutamate a precursor for arginine? Have been scratching my head about this mainly because of that extra CH2 group arg has. Any insight appreciated

[Babcock_Hall]

Suppose that you were able to protect the amino nitrogen and then reduce this derivative of glutamate at C-1.  What could happen next?

[orgo814]

Not sure what you mean. Protect amino?

[kriggy]

Suppose that you were able to protect the amino nitrogen and then reduce this derivative of glutamate at C-1.  What could happen next?

Protect so it doesnt form cyclic product?

Not sure what you mean. Protect amino?

http://en.wikipedia.org/wiki/Protecting_group

Might help understand what is ment by protecting.
its not that the arginine is formed in single step, its more of reaction sequence with several intermediates

[Babcock_Hall]

butlerw2,

The biosynthesis of arginine from glutamate is indeed a multistep pathway.  In the first step, glutamate is converted to N-acetylglutamate, and the acetyl group is removed at the end of the biosynthesis.  The textbook explanation of why the acetylation takes place is to prevent an unwanted side-reaction (cyclization) once the gamma-carboxylate group is reduced to an aldehyde.  Offhand, this is the only example I can think of where nature uses protecting group chemistry, but there must be others.