Allothreonine aldolase

The L-threonine (EC 4.1.2.5), D-threonine (EC 4.1.2.-) or L-allothreonine aldolases (EC 4.1.2.6 synonymous to S1IMT) can be used for resolution of racemic (allo)threonine mixtures by highly selective cleavage of the unwanted isomers42, but can also efficiently direct the anabolic pathways. The substrate spectrum includes propanal, butanal and dodecanal43. 

Rat liver aminomalonate decarboxylase has recently been identified with cytoplasmic serine hydroxymethylase and allothreonine aldolase 17>. Most references in this narrative have been omitted, since they can all be found in Popjack s review t). 

Palekar, A. G., Tate, S. S., Meister, A. Rat liver aminomalonate decarboxylase. Identity with cytoplasmic serine hydroxymethylase and allothreonine aldolase. J. Biol. Chem. 248, 1158-1167 (1973). 

When hydroxyaldehydes are employed as L-Thr aldolase substrates, complex product mixtures result. Protection of the hydroxyl groups prevents this, and allowes the preparation of C4-protected L-threonine and L-allothreonine derivatives. Acceptor aldehydes with an oxygen functionality at the a-position gave high erythro/threo... 

About a twentyfold enhancement in enzyme activity on allothreonine and a thirty-fivefold on threonine has been obtained. The threonine aldolases are quite unstable enzymes and do not lend themselves readily to extensive piuification. 

Both threonine aldolases were demonstrated to be pyridoxal phosphate-dependent and to be sulfhydryl enzymes. Michaelis constants were calculated to have the values of 69 X 10 M for L-threonine and 4.25 X 10 M for L-allothreonine. 

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