|Gene:||TSBType2||Accession Number: AT5G38530 (MetaCyc)|
Species: Arabidopsis thaliana col
Subunit composition of
tryptophan synthase = [TSBType2]2
trytophan synthase, beta subunit = TSBType2
TSBType2 is a tryptophan synthase, beta subunit (TSB) (type 2) enzyme that catalyzes the condensation of serine and indole to form tryptophan in vitro [Yin10]. Although there are several other TSB enzymes in Arabidopsis, including TSB1, they belong to the type 1 portion of the enzyme family. Land plants as far back as mosses at least, have had members of both types of TSBs present in their genomes. In most organs, TSBtype2 is transcripts are expressed at a lower level than TSB1but in dry seeds they are expressed at comparable levels [Yin10].
This enzyme has a remarkably low Km of 74 +/- 12 nM for indole, but it has a much higher Km of 35 mM for L-serine. No serine deaminase activity has been observed for the TSBType2 enzyme in vitro [Yin10].
Size exclusion chromatography indicates that this protein purifies at a weight that is consistent with it forming a homodimer, similar to other microbial type 2 TSB enzymes that have been previously characterized [Yin10].
Its biological role has not yet been determined, but it has a very high affinity for indole which may be involved in allowing TSBtype2 to carefully limit free indole build-up. But, to date no overall change in plant morphology or seedling root growth have been observed in tsbtype2 mutants, indicating that this gene is not essential under optimum conditions [Yin10].
Molecular Weight of Multimer: 90.0 kD (experimental) [Yin10]
Enzymatic reaction of: tryptophan synthase
EC Number: 126.96.36.199L-serine + indole → L-tryptophan + H2O
The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the Enzyme Commission system.
The reaction is favored in the direction shown.
In Pathways: L-tryptophan biosynthesis
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