Question

What is the rate limiting step in biosynthesis? Reactions can be found here http://upload.wikimedia.org/wikipedia/en/thumb/7/7e/Met_biosynthesis.gif/500px-Met_biosynthesis.gif
and the enzymes involved are
1.Aspartokinase
2.Aspartate-semialdehyde_dehydrogenase
3.Homoserine dehydrogenase
4.Homoserine O-transsuccinylase
5.Cystathionine-γ-synthase
6.Cystathionine-β-lyase
7.Methionine synthase (in mammals, this step is performed by Homocysteine methyltransferase or Betaine—homocysteine S-methyltransferase)

Answer 1

Consider which step in the biosynthesis of methionine is irreversible. In other words, the committed step.

Answer 2

@abb0t would that be the first reaction?

Answer 3

i know what a committed step is, but i have trouble figuring out which one it is

Answer 4

I don't know, I am asking you. You are probably more familiar with the biochemical pathway of the biosynthesis of Met than I am.

Answer 5

I have a strong feeling that it may be step 4. But I am not sure.
If this is what you were asked to research though, I think you should look into this on your own. I don't really deal with metabolic biochemistry much.
If you find more information, please do post though.

Answer 6

@abb0t it is step 5 lol

Answer 7

thanks tho

Answer 8

Yeah, 4 or 5. The binding of two. makes sense.