Pseudaminic acid synthase (, PseI, NeuB3) is an enzyme with systematic name phosphoenolpyruvate:2,4-bis(acetylamino)-2,4,6-trideoxy-beta-L-altropyranose transferase (phosphate-hydrolysing, 2,7-acetylamino-transferring, 2-carboxy-2-oxoethyl-forming). This enzyme catalyses the following chemical reaction
The enzyme requires a divalent metal ion, preferably Mn<sup>2+</sup> and Co<sup>2+</sup>.