Function
Its primary function is to catalyze the reversible interconversion of serine and glycine with tetrahydrofolate (THF) serving as the one-carbon carrier. This reaction serves as the major source of one-carbon groups required for the biosynthesis of purines, thymidylate, methionine, and other important biomolecules. Also exhibits THF-independent aldolase activity toward beta-hydroxyamino acids, producing glycine and aldehydes, via a retro-aldol mechanism. Thus, is able to catalyze the cleavage of L-threonine, L-allo-threonine, L-threo-beta-phenylserine and L-erythro-beta-phenylserine. This second activity is likely to be physiological in H.thermophilus, which is an organism that lacks the ortholog gene for the 'real' threonine aldolase characterized in mesophilic bacteria (LtaE), yeast and plants.
Sequence
MRHLFNTDAEIYEAIVKEYERQFYHLELIASENFTSLAVMEAQGSVMTNKYAEGLPHKRYYGGCEFVDIAEDLAIERAKALFDAEHANVQPHSGTQANMAVYMAVLKPGDTIMGMDLSHGGHLTHGAKVNFSGKIYNAVYYGVHPETHLIDYDQLYRLAKEHKPKLIVGGASAYPRVIDWAKLREIADSVGAYLMVDMAHYAGLIAGGVYPNPVPYAHFVTSTTHKTLRGPRSGFILCKKEFAKDIDKSVFPGIQGGPLMHVIAAKAVAFKEAMSQEFKEYARQVVANARVLAEEFIKEGFKVVSGGTDSHIVLLDLRDTGLTGREVEEALGKANITVNKNAVPFDPLPPVKTSGIRLGTPAMTTRGMKEDQMRIIARLISKVIKNIGDEKVIEYVRQEVIEMCEQFPLYPELREEINHLAKIKATY