Editing Tryptophan synthase (section)

==Enzyme mechanism==
[[Image:Tryptophan Synthase Mechanism 5.gif|thumb|left|alt=caption.|Proposed mechanism of tryptophan synthase]]The net reaction of tryptophan synthase turns indole-3-glycerol phosphate and serine into glyceraldehyde-3-phosphate, tryptophan and water. The reaction happens in two steps, each catalyzed by one of the subunits:[[Image:Tryptophan synthetase rn.png|thumb|500px|Reaction catalyzed by tryptophan synthase|center]]

=== α subunit reaction ===
The α subunit catalyzes the formation of indole and G3P from a retro-aldol cleavage of IGP. The αGlu49 and αAsp60 are thought to be directly involved in the catalysis as shown.<ref name="Overview" /> The rate limiting step is the isomerization of IGP.<ref name="a Rate Limiting Step">{{cite journal |vauthors=Anderson KS, Miles EW, Johnson KA | author-link2=Edith Wilson Miles|title = Serine modulates substrate channeling in tryptophan synthase. A novel intersubunit triggering mechanism | journal = J Biol Chem | volume = 266 | issue = 13 | pages = 8020–33 |date=May 1991 | doi=10.1016/S0021-9258(18)92934-0| pmid = 1902468 | doi-access=free}}</ref> See image 2.

=== β subunit reaction ===
The β subunit catalyzes the β-replacement reaction in which indole and serine condense to form tryptophan in a PLP dependent reaction. The βLys87, βGlu109, and βSer377 are thought to be directly involved in the catalysis as shown.<ref name="Overview" /> Again, the exact mechanism has not been conclusively determined. See image 2.